2012 Henry Efficient Hybrid Solar Cells Based On

8/9/2019 2012 Henry Efficient Hybrid Solar Cells Based On

1/12

Reports

An efficient solar cell must absorb over a broad spectral range, from thevisible to near infrared region (350 to ~ 950 nm), and convert the inci-dent light effectively into charges. The charges must be collected at ahigh voltage with suitable current in order to do useful work (18). Asimple measure of solar cell effectiveness at generating voltage is thedifference in energy between the optical band gap of the absorber andthe open-circuit voltage (Voc) generated by the solar cell under simulatedAM1.5G 100 mW cm2 solar illumination (9). For instance, gallium

arsenide, GaAs, solar cells exhibit Vocof 1.11 V and an optical band gap of1.4 eV giving a difference of approxi-mately 0.29 eV (2). For dye-sensitizedand organic solar cells, this differenceis usually on the order of 0.7 to 0.8 eV(2, 9). For organic solar cells, such

losses are predominantly caused bytheir low dielectric constants. Tightly-bound excitons form that require aheterojunction with an electron accep-tor with a significant energy offset toenable ionization and charge separation(10, 11). Likewise, dye-sensitized solarcells (DSSCs) have losses, both fromelectron transfer from the dye (or ab-sorber) into the TiO2which requires acertain driving force and from dyeregeneration from the electrolyte whichrequires an over potential. Effortshave been made to reduce such lossesin the DSC by moving from a multi-

electron iodide/tri-iodide redox coupleto one-electron outer-sphere redoxcouples, such as a cobalt complexes ora solid-state hole-conductor (1, 4, 12,13).

Recently, there has been mountinginterest in inorganic semiconductorsensitized solar cells, (14, 15). Anextremely thin absorber (ETA) layer, 2to 10 nm in thickness is coated upon

the internal surface of a mesoporous TiO2electrode and then contactedwith an electrolyte or solid-state hole-conductor. These devices haveachieved power conversion efficiencies of up to 6.3% (15). However, theETA concept suffers from rather low Voc ; the problem may lie in the

electronically disordered, low mobility n-type TiO2(16). Perovskites arerelatively underex-plored alternatives(Fig. 1A) that pro-

Efficient Hybrid Solar Cells Based on

Meso Superstructured Organometal

Halide Perovskites

Michael M. Lee,1Jol Teuscher,1Tsutomu Miyasaka,2Takurou N. Murakami,2,3Henry J. Snaith1*1Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, UK.

2Graduate

School of Engineering, Toin University of Yokohama, 1614 Kurogane, Aoba, Yokohama 225-8503, Japan.3Research Center for Photovoltaic Technologies, National Institute of Advanced Industrial Science and

Technology, Central 5, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan.

*To whom correspondence should be addressed. E-mail: [email protected]

The energy cost associated with separating tigh tly-bound excitons , photo-generated electron-hole pairs, and extracting free charges from high ly diso rderedlow mobility networks represent fundamental losses for many low-cost photovoltaictechnologies. We report a low -cost, solution-processable solar cell based on ahighly c rystalline perovskite absorber wit h intense visible-to-near-infraredabsorptivity that has a power conversion efficiency of 10.9% in a single junc tiondevice under simulated full sunlight. This meso-superstructured solar cell (MSSC)exhibits exceptionally few fundamental energy losses illustrated by generatingopen-circuit photovoltages of over 1.1 volts, despite the relatively narrow absorberband gap of 1.55 electron vol ts. The functionality arises from the use ofmesoporous alumina as an inert scaffold which structures the absorber and forceselectrons to reside in and be transported through the perovskite.

Fig. 1. (A) Three-dimensional schematicrepresentation of perovskite structure,

ABX3where A = CH3NH3, B = Pb, and X= Cl, I (left) with two-dimensionalschematic illustrating the perovskite unitcell (right). (B) UV-Vis absorbancespectra of the photoactive layer in thesolar cell (mesoporous oxide; perovskiteabsorber; spiro-OMeTAD) sealedbetween two sheets of glass in nitrogenand exposed to simulated AM1.5Gsunlight at 100 mW cm

2irradiance for up

to 1000 hours. No additional UV filtrationwas used for the solar irradiance. Inset isthe extracted optical density at 500 nm asa function of time. (C) Schematicrepresentation of full device structure,where the mesoporous oxide is either

Al2O3 or anatase TiO2 (left), Cross-sectional SEM image of a full deviceincorporating mesoporous Al2O3 (right).Scale bar represents 500 nm. SEMmeasurements were taken using JEOLJSM 7500F.

/ http://www.sciencemag.org/content/early/recent/ 4 October 2012 / Page 1/ 10.1126/science.1228604

onOctober

13,

2012

www.sciencemag.org

Downloadedfrom
http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/


2/12

Fig. 2. (A) IPCE action spectrum of an Al2O3based and perovskite sensitized TiO2solar cell, with device structure: FTO/Compact-TiO2/Mesoporous Al2O3 (red trace with crosses) or mesoporous TiO2 (black trace with circles)/ CH3NH3PbI2Cl/Spiro-OMeTAD/Ag(B) Current-Voltage characteristics under simulated AM1.5G 100 mW cm

2 illumination for Al2O3based cells, one cell exhibiting

high efficiency (red solid trace with crosses) and one exhibiting greater than 1.1 V VOC(red dashed line with crosses), perovskiteTiO2 sensitized solar cell (black trace with circles), and a planar-junction diode with a structure FTO/compact TiO2/CH3NH3PbI2Cl/Spiro-OMeTAD/Ag (purple trace with squares).

vide a framework for binding the organic and inorganic components intoa molecular composite. Given careful consideration of the interaction

between organic-inorganic elements and by controlling the size-tunablecrystal cell (17) it is possible to create new and interesting materialsusing rudimentary wet chemistry. Era, Mitzi, and co-workers haveshown that layered perovskites based on organometal halides demon-strate excellent performance as light-emitting diodes (18, 19) and tran-sistors with mobilities comparable to amorphous silicon (20).Organometal halide perovskites have been used as sensitizers in liquidelectrolyte based photo-electrochemical cells with conversion efficien-cies between 3.5 to 6.5% (21, 22). Recently, a CsSnI3 perovskite has

been shown to function efficiently as a hole-conductor in solid-state dye-sensitized solar cells, delivering up to 8.5% power conversion efficiency(23, 24).

We report on a solution-processable solar cell that overcomes thefundamental losses of organic absorbers and disordered metal oxides.We followed the ETA approach and used a perovskite absorber andmesoporous TiO2 as the transparent n-type component, and 2,2(7,7(-tetrakis-(N,N-di-pmethoxyphenylamine)9,9(-spirobifluorene))) (spiro-OMeTAD) as the transparent p-type hole conductor. These devices ex-hibited power conversion efficiencies near 8%. Remarkably, we alsofound replacing the mesoporous n-type TiO2with insulating Al2O3, im-

proved the power conversion efficiency. The Al2O3 is a wide band gap(7 to 9eV) insulator and purely acts as a scaffold upon which the

perovskite is coated. We observe that electron transport through theperovskite layer is much faster than through the n-type TiO2. In addition,we observe a few hundred millivolt increase in Voc moving from the

TiO2 to the insulating Al2O3 scaffold, and a record power conversionefficiency of 10.9% under simulated Air Mass (AM)1.5 full sun illumi-nation.

The specific perovskite we used is of mixed-halide form:methylammonium lead iodide chloride, (CH3NH3PbI2Cl), which was

processed from a precursor solution inN,N-dimethylformamide via spin-coating in ambient conditions. X-ray diffraction analysis forCH3NH3PbI2Cl prepared on glass (fig. S1) (25), showed diffraction

peaks at 14.20, 28.58, 43.27 we assigned as the (110), (220), and (330)planes, respectively, of a tetragonal perovskite structure with lattice pa-rameters a = 8.825 , b = 8.835 , c = 11.24 , similar to theCH3NH3PbI3previously reported (21). The extremely narrow diffraction

peaks suggest that the films have long range crystalline domains (greaterthan 200 nm, peak width limited by instrument broadening) and arehighly oriented with the a-axis (21, 26). In contrast to themethylammonium tri-halogen plumbates previously reported in solarcells (i.e., CH3NH3PbI3) (21, 22), this iodide-chloride mixed-halide

perovskite was remarkably stable to processing in air. In Fig. 1B, theabsorption spectra demonstrated good light harvesting capabilities overthe visible to near-infrared (near-IR) spectrum, and was also stable to

prolonged light exposure, as demonstrated by 1000 hours constant illu-mination under full sunlight. Negligible change in absorbance is illus-trated by the inset to Fig. 1B, where the absorbance of the film at 500 nmremained around 1.8 throughout the entire measurement period (absorb-ance of 1.8 corresponds to 98.4% absorbance). We note that the scale isoptical density, where absorbance of ~ 0.5 at 700 nm corresponds toaround 70% attenuation in a single pass, and in the solar cell, there aretwo passes of light leading to approximately 91% absorbance at thiswavelength.

The solar cells were fabricated on semi-transparent fluorine dopedtin oxide (FTO) coated glass, coated with a compact layer of TiO2thatacts as an anode. The porous oxide films were fabricated from sol-gel

processed sintered nanoparticles. The perovskite precursor solution wasinfiltrated into the porous oxide mesostructure via spin-coating, and wasdried at 100C which enabled the perovskite to form via self-assembly ofthe constituent ions. Dark coloration was only observed after this dryingstep.

To elaborate upon the perovskite coating process, there has been ex-tensive work done on investigating how solution-cast materials infiltrate

into mesoporous oxides (2732). If the concentration of the solution islow enough, and the solubility of the cast material high enough, the ma-terial will completely penetrate the pores as the solvent evaporates. Typ-ically, the material forms a wetting layer upon the internal surface ofthe mesoporous film that uniformly coats the pore walls throughout thethickness of the electrode (2831). The degree of pore-filling can becontrolled by varying the solution concentration (2932). If the concen-tration of the casting solution is high, then maximum pore filling occurs,and any excess material forms a capping layer on top of the filledmesoporous oxide.

For the optimum perovskite precursors concentrations we used, therewas no appearance of a capping layer, which implies that the perovskite


onOctober

13,

2012

www.sciencemag.org

Downloadedfrom
http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/


3/12

was predominantly formed within the mesoporous film. We verified thatthe perovskite was within and uniformly distributed throughout themesoporous oxide films by performing cross-sectional scanning electron

microscopy (SEM) with elemental mapping via energy dispersive x-ray(EDX) analysis (fig. S2) (25). To complete the photoactive layer, the

perovskite coated porous electrode was further filled with the hole-transporter, spiro-OMeTAD, via spin-coating (Fig. 1C). It is apparent inFig. 1C, that the spiro-OMeTAD has formed a capping layer, whichensure selective collection of holes at the silver electrode.

In Fig. 2A, the incident photon-to-electron conversion efficiency

(IPCE) action spectrum is shown for the devices that use mesoporousTiO2and Al2O3, exhibiting spectral sensitivity spanning from the visibleto the near-IR (400 to 800 nm) with a peak IPCE of over 80% for bothoxides. The slight difference in shape arose from the slightly different

perovskite concentrations in the optimized devices. In Fig. 2B, we showcurrent-voltage (J-V) curves measured under simulated AM1.5 100mW/cm2 illumination. The sensitized TiO2solar cell exhibited a short-circuit photocurrent (Jsc) of 17.8 mA cm

2, a Vocof 0.80 V with a fillfactor of 0.53 yielding an overall power conversion efficiency () of7.6%. We present two different J-V curves for the Al2O3based device.The most efficient device exhibited a Jscof 17.8 mA cm

2, a Vocof 0.98V with a fill factor of 0.63 yielding an of 10.9%. The third curve,dashed trace, shows a device with respectable Jscof 15.4 mA cm

2andvery high Vocof 1.13 V but a low fill factor of 0.45, yielding an overall

power conversion efficiency of 7.8%. In the SOM we show histograms

of device performance parameters for the TiO2and Al2O3based devices(fig. S3) (25). The general trend is that the Al2O3cells generated over200 mV higher open-circuit voltages than the sensitized TiO2solar cells,with comparable short-circuit currents and slightly lower fill factors.From the solar cell measurements on alumina-based devices, it was ap-

parent that the perovskite layer could function as both absorber and n-type component, transporting electronic charge out of the device. Wefurther illustrate the semiconducting nature of the perovskite by theconstruction of a planar-junction diode with a structure FTO/compactTiO2/ CH3NH3PbI2Cl/Spiro-OMeTAD/Ag. The perovskite film wasapproximately 150 nm thick in this configuration, and the solar cell gen-erated Jscof 7.13 mA cm

2Vocof 0.64 V fill factor of 0.4 and of 1.8%.If we take the optical band gap of CH3NH3PbI2Cl to be 1.55eV from

the IPCE onset at 800nm (33), and the open-circuit voltage to be 1.1V,

this represents a difference in energy of only 0.45eV, competitive withthe best thin film technologies (2). To understand why we observed sucha dramatic increase in voltage over the TiO2cells, we need to considerthe operational mode of the two concepts (Fig. 3A). We would expectfor sensitized TiO2devices, after light absorption in the perovskite, elec-trons would be transferred to the TiO2with subsequent electron transportto the FTO electrode through the TiO2, and holes to the spiro-OMeTADwith subsequent transport to the silver electrode. For Al2O3based cells,the electrons must remain in the perovskite phase (34), until they arecollected at the planar TiO2 coated FTO electrode, and must hence betransported throughout the film thickness in the perovskite. Hole-transferfrom the photoexcited perovskite should occur to the spiro-OMeTAD inmuch the same way as in the sensitized device. We confirm that Al2O3does not act as an n-type oxide in DSSCs in fig. S4 (25).

Fig. 3. (A) Cartoon illustrating the charge transfer andtransport in a perovskite sensitized TiO2solar cell, (left) and anon-injecting Al2O3 based perovskite solar cell, (right). (B)Photo-induced absorbance (PIA) spectra of the mesoporousTiO2(black open circles) and Al2O3(red crosses) films coatedwith perovskite with (solid lines) and without (dashed lines)spiro-OMeTAD hole transporter. ex= 496.5 nm, repetition rate23 Hz. (C) Charge transport lifetime determined by smallperturbation transient photocurrent decay of perovskitesensitized TiO2 (circles with black line to aid the eye) and

Al2O3cells (red crosses with line to aid the eye). Inset showsnormalised photocurrent transients for Al2O3 (red trace withcrosses every 7

th point) and TiO2 (black trace with circles

every 7thpoint) cells, set to generate 5 mA cm

2photocurrent

from the background light bias.

In order to examine the charge generation in these devices, we per-

formed photoinduced absorption (PIA) spectroscopy on the oxide filmscoated with the perovskite, both with and without the addition of spiro-OMeTAD. For the mesoporous TiO2 film coated with perovskite, thePIA spectrum revealed features in the near infrared assigned to the freeelectrons in the titania (35), confirming effective sensitization of thetitania by the perovskite. In contrast, films made of Al2O3coated with

perovskite exhibit no PIA signal, confirming the insulating role of alu-mina. After addition of spiro-OMeTAD, we could efficiently monitor theoxidized species of spiro-OMeTAD created after photoexcitation of the

perovskite. They had absorption features at 525 and 750 nm, as well as abroad band around 1200 nm, assigned to the hole located on thetriarylamine moieties (28, 36), which dominate the spectra in both the


onOctober

13,

2012

www.sciencemag.org

Downloadedfrom
http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/


4/12

TiO2and Al2O3based samples. These results indicate that hole-transferis highly effective from the photoexcited perovskite to spiro-OMeTAD,and specifically that a hole-conductor is required to enable long livedcharge species within the perovskite coated on the Al2O3. We note thatthe PIA signal depended both on the concentration and lifetime of thespecies monitored, hence from this measurement alone quantification ofthe relative charge generated yield is not possible.

In order to probe the effectiveness of the perovskite layer at trans-porting electronic charge out of the device, we performed small pertur-bation transient photocurrent decay measurements (37). The solar cellswere exposed to simulated sun light and flashed with a small red light

pulse, the decay rate of the transient photocurrent signal is approximate-ly proportional to the rate of charge transport out of the photoactive layer(37). In Fig. 3C, we observed over tenfold faster charge collection in theAl2O3based devices than in the TiO2based sensitized devices indicatingfaster electron diffusion through the perovskite phase, than through then-type TiO2.

Because there was no n-type oxide in the Al2O3based cells, the de-vices were no longer sensitized solar cells, but are now a two-component hybrid solar cell. As designed, the Al2O3is simply acting asa meso-scale scaffold upon which the device is structured, we termthis concept a meso-superstructured solar cell (MSSC). The above

measurements demonstrate that long-lived charge carriers can be gener-ated via hole-transfer from the perovskite to spiro-OMeTAD, and thatthe perovskite layer is faster at transporting electronic charge than themesoporous TiO2. However, they do not explain the increase in Voc: TheVoc is generated by the buildup of electrons in the n-type material andholes in the p-type material, resulting in splitting of the quasi Fermi lev-els for both electrons and holes. For mesoporous TiO2there exist sites inthe tail of the density of states which extend into the band gap (38). The-se fill with electrons under illumination, and result in the quasi Fermilevel for electrons (EFn*) being further from the conduction band for anygiven charge density, than would the case be if these states did not exist,i.e., in a crystalline semiconductor. The increased charge storing capaci-ty of materials with a high density of sub-band gap states is termedchemical capacitance (38). There is, in essence, no chemical capaci-

tance of the Al2O3, and for the MSSCs all the electronic charge residesin the perovskite, moving the EFn* in this material nearer the conductionband for the same charge density. The higher voltage indicates that thereare fewer surface and sub-band gap states in the perovskite films than inthe mesoporous TiO2. Hence, the increased voltage is caused by a sub-stantial reduction of the chemical capacitance of the solar cell. We useda compact layer of TiO2as the electron selective anode, but the chemicalcapacitance of this extremely thin (50 to 100nm) TiO2 layer was verylow because of the low surface area (i.e., flat). In addition, the compactlayer deposited via spray pyrolysis has a donor density of around 1018cm3(39), and the sub-band gap sites responsible for the chemical capac-itance may be full.

A central question is whether the MSSC is excitonic or a distributedp-n junction. The perovskites tend to form layered structures, with con-tinuous 2D metal halide planes perpendicular to the z-axis, and the lower

dielectric organic components (methyl amine) between these planes. Thequasi 2D confinement of the excitons results in an increased exciton

binding energy which can be up to a few hundred meV (40). The reason-ably high photocurrents from the planar junction solar cells (Fig. 2B)could be explained by either moderately delocalized and highly mobileexcitons being quenched at the perovskite spiro-OMeTAD interface, orthe generation of free charges in the bulk of the perovskite films withreasonably good electron and hole-migration out of the devices.

The key limitation in performance of the MSSC at present is a bal-ance between series and shunt resistance. The perovskite absorber isreasonably conductive, measured to be on the order of 103S cm3, thusshort-circuiting of the device occurs if contact exists between the silver

electrode and the perovskite absorber. A thick capping layer of p-typespiro-OMeTAD readily resolves this issue, however; spiro-OMeTAD isless conductive (~105S cm1) so a thicker capping layer results in highseries resistance, thus we are presented with a compromise.

In summary, we have evolved the solid-state sensitized solar cell in-to a new concept with low fundamental losses. The application of amesostructured insulating scaffold upon which extremely thin films of n-

type and p-type semiconductors are assembled, termed the meso-superstructured solar cell (MSSC), has proven to be extraordinarily ef-fective with an n-type perovskite, delivering over 10.9% power conver-sion efficiency under full sun illumination. Further advances in overall

power conversion efficiency are expected by extending the absorptiononset toward 940 nm, through the implementation of new perovskites or

broadening this concept to other solution-processable semiconductors.Enhancing the light absorption near the band edge through carefullyengineered mesostructures or better photon management would lead toincreased photocurrent. Reduced series resistance through the utilizationof higher mobility hole-transporters, or better control over the cappinglayer thickness would improve the fill factor. Finally, extending thissystem to multi-junction devices, notably without the requirement forlattice matching, would further enhance performance.

References and Notes1. B. ORegan, M. Grtzel, A low-cost, high-efficiency solar cell based on dye-

sensitized colloidal TiO2 films. Nature 353, 737(1991). doi:10.1038/353737a0

2. M. A. Green, K. Emery, Y. Hishikawa, W. Warta, E. D. Dunlop, Solar cellefficiency tables (version 39). Prog. Photovolt. Res. Appl. 20, 12(2012). doi:10 002/pip.2163.1

3. L. Han et al., High-efficiency dye-sensitized solar cell with a novel co-adsorbent.Energy Environ. Sci.5, 6057 (2012). doi:10.1039/C2EE03418B

4. A. Yella et al., Porphyrin-sensitized solar cells with cobalt (II/III)-based redoxelectrolyte exceed 12 percent efficiency. Science 334, 629(2011). doi:10.1126/science.1209688Medline

5. G. Yu, J. Gao, J. C. Hummelen, F. Wudl, A. J. Heeger, Polymer photovoltaiccells: Enhanced efficiencies via a network of internal donor-acceptorheterojunctions. Science 270, 1789(1995). doi:10.1126/science.270.5243.1789

6. J. J. M. Halls et al., Efficient photodiodes from interpenetrating polymernetworks.Nature376, 498 (1995). doi:10.1038/376498a0

7. A. H. Ip et al., Hybrid passivated colloidal quantum dot solids.Nature Nano.7,577 (2012). doi:10.1038/nnano.2012.127

8. T. K. Todorov, K. B. Reuter, D. B. Mitzi, High-efficiency solar cell with earth-abundant liquid-processed absorber. Adv. Mater. 22, E156(2010). doi:10.1002/adma.200904155

9. H. J. Snaith, Estimating the maximum attainable efficiency in dye-sensitizedsolar cells.Adv. Funct. Mater.20, 13 (2010). doi:10.1002/adfm.200901476

10. G. Dennler, M. C. Scharber, C. J. Brabec, Polymer-fullerene bulk-heterojunction solar cells. Adv. Mater. 21, 1323(2009). doi:10.1002/adma.200801283

11. B. E. Hardin, H. J. Snaith, M. D. McGehee, The renaissance of dye-sensitizedsolar cells.Nat hotonics6, 162 (2012).. P doi:10.1038/nphoton.2012.22

12. U. Bach et al., Solid-state dye-sensitized mesoporous TiO2 solar cells withhigh photon-to-electron conversion efficiencies. Nature 395, 583

(1998). doi:10.1038/2693613. J. Burschka et al., Tris(2-(1H-pyrazol-1-yl)pyridine)cobalt(III) as p-type

dopant for organic semiconductors and its application in highly efficient solid-state dye-sensitized solar cells. J. Am. Chem. Soc. 133, 18042(2011). doi:10.1021/ja207367tMedline

14. Y. Itzhaik, O. Niitsoo, M. Page, G. Hodes, Sb2S3-sensitized nanoporous TiO2solar cells.J. Phys. Chem. C113, 4254 (2009). doi:10.1021/jp900302b

15. J. A. Chang et al., Panchromatic photon-harvesting by hole-conductingmaterials in inorganic-organic heterojunction sensitized-solar cell through theformation of nanostructured electron channels. Nano Lett. 12, 1863(2012). doi:10.1021/nl204224vMedline

16. J. Nelson, Continuous-time random-walk model of electron transport innanocrystalline TiO2 electrodes. Phys. Rev. B 59, 15374


onOctober

13,

2012

www.sciencemag.org

Downloadedfrom
http://dx.doi.org/10.1038/353737a0http://dx.doi.org/10.1038/353737a0http://www.sciencemag.org/http://dx.doi.org/10.1002/pip.2163http://dx.doi.org/10.1002/pip.2163http://dx.doi.org/10.1002/pip.2163http://www.sciencemag.org/http://dx.doi.org/10.1126/science.1209688http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=22053043&dopt=Abstracthttp://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=22053043&dopt=Abstracthttp://www.sciencemag.org/http://dx.doi.org/10.1126/science.270.5243.1789http://dx.doi.org/10.1126/science.270.5243.1789http://dx.doi.org/10.1038/376498a0http://dx.doi.org/10.1038/376498a0http://dx.doi.org/10.1002/adma.200904155http://dx.doi.org/10.1002/adma.200904155http://dx.doi.org/10.1002/adfm.200901476http://dx.doi.org/10.1002/adfm.200901476http://dx.doi.org/10.1002/adma.200801283http://dx.doi.org/10.1002/adma.200801283http://dx.doi.org/10.1038/nphoton.2012.22http://dx.doi.org/10.1038/nphoton.2012.22http://dx.doi.org/10.1038/26936http://dx.doi.org/10.1038/26936http://dx.doi.org/10.1021/ja207367thttp://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=21972850&dopt=Abstracthttp://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=21972850&dopt=Abstracthttp://dx.doi.org/10.1021/jp900302bhttp://dx.doi.org/10.1021/jp900302bhttp://dx.doi.org/10.1021/nl204224vhttp://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=22401668&dopt=Abstracthttp://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=22401668&dopt=Abstracthttp://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=22401668&dopt=Abstracthttp://dx.doi.org/10.1021/nl204224vhttp://dx.doi.org/10.1021/jp900302bhttp://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=21972850&dopt=Abstracthttp://dx.doi.org/10.1021/ja207367thttp://dx.doi.org/10.1038/26936http://dx.doi.org/10.1038/nphoton.2012.22http://dx.doi.org/10.1002/adma.200801283http://dx.doi.org/10.1002/adfm.200901476http://dx.doi.org/10.1002/adma.200904155http://dx.doi.org/10.1038/376498a0http://dx.doi.org/10.1126/science.270.5243.1789http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=22053043&dopt=Abstracthttp://dx.doi.org/10.1126/science.1209688http://dx.doi.org/10.1002/pip.2163http://dx.doi.org/10.1038/353737a0


5/12


(1999). doi:10.1103/PhysRevB.59.1537417. D. B. Mitzi, C. A. Field, W. T. A. Harrison, A. M. Guloy, Conducting tin

halides with a layered organic-based perovskite structure. Nature 369, 467(1994). doi:10.1038/369467a0

18. K. Chondroudis, D. B. Mitzi, Electroluminescence from an organicinorganicperovskite incorporating a quaterthiophene dye within lead halide perovskitelayers. Chem. Mater.11, 3028 (1999). doi:10.1021/cm990561t

19. M. Era, T. Tsutsui, S. Saito, Polarized electroluminescence from oriented p-

sexiphenyl vacuum-deposited film. Appl. Phys. Lett. 67, 2436(1995). doi:10.1063/1.114599

20. C. R. Kagan, D. B. Mitzi, C. D. Dimitrakopoulos, Organic-inorganic hybridmaterials as semiconducting channels in thin-film field-effect transistors.Science286, 945 (1999). doi:10.1126/science.286.5441.945Medline

21. A. Kojima, K. Teshima, Y. Shirai, T. Miyasaka, Organometal halideperovskites as visible-light sensitizers for photovoltaic cells. J. Am. Chem.Soc.131, 6050 (2009). doi:10.1021/ja809598rMedline

22. J. H. Im, C. R. Lee, J. W. Lee, S. W. Park, N. G. Park, 6.5% efficientperovskite quantum-dot-sensitized solar cell. Nanoscale 3, 4088(2011). doi:10.1039/c1nr10867kMedline

23. I. Chung, B. Lee, J. He, R. P. H. Chang, M. G. Kanatzidis, All-solid-state dye-sensitized solar cells with high efficiency. Nature 485, 486(2012). doi:10.1038/nature11067Medline

24. H. J. Snaith, How should you measure your excitonic solar cells? EnergyEnviron. Sci.5, 6513 (2012). doi:10.1039/C2EE03429H

25. See supplementary materials on ScienceOnline.26. A. Poglitsch, D. Weber, Dynamic disorder in

methylammoniumtrihalogenoplumbates (II) observed by millimeter-wavespectroscopy.J. Chem. Phys.87, 6373 (1987). doi:10.1063/1.453467

27. T. Leijtens et al., Hole transport materials with low glass transitiontemperatures and high solubility for application in solid-state dye-sensitizedsolar cells.ACS Nano6, 1455 (2012). doi:10.1021/nn204296bMedline

28. H. J. Snaith et al., Charge collection and pore filling in solid-state dye-sensitized solar cells. Nanotechnology19, 424003 (2008). doi:10.1088/0957-4484/19/42/424003Medline

29. J. Melas-Kyriazi et al., The effect of hole transport material pore filling onphotovoltaic performance in solid-state dye-sensitized solar cells.Adv. EnergyMater.1, 407 (2011). doi:10.1002/aenm.201100046

30. A. Abrusci et al., Facile infiltration of semiconducting polymer intomesoporous electrodes for hybrid solar cells. Energy Environ. Sci. 4, 3051(2011). doi:10.1039/C1EE01135A

31. I.-K. Ding et al., Pore-filling of spiro-OMeTAD in solid-state dye sensitizedsolar cells: Quantification, mechanism, and consequences for deviceperformance. Adv. Funct. Mater. 19, 2431(2009). doi:10.1002/adfm.200900541

32. P. Docampo et al., Pore filling of spiro-OMeTAD in solid-state dye-sensitizedsolar cells determined via optical reflectometry. Adv. Funct. Mater. n/a(2012). doi:10.1002/adfm.201201223Medline

33. D. A. R. Barkhouse, O. Gunawan, T. Gokmen, T. K. Todorov, D. B. Mitzi,Device characteristics of a 10.1% hydrazine-processed Cu2ZnSn(Se,S)4 solarcell. Prog. Photovolt. Res. Appl.20, 6 (2012). doi:10.1002/pip.1160

34. A. Kojima, M. Ikegami, K. Teshima, T. Miyasaka, Highly luminescent leadbromide perovskite nanoparticles synthesized with porous alumina media.Chem. Lett.41, 397 (2012). doi:10.1246/cl.2012.397

35. G. Rothenberger, D. Fitzmaurice, M. Graetzel, Spectroscopy of conductionband electrons in transparent metal oxide semiconductor films: Opticaldetermination of the flatband potential of colloidal titanium dioxide films. J.

Phys. Chem.96, 5983 (1992). doi:10.1021/j100193a06236. G. Boschloo, A. Hagfeldt, Photoinduced absorption spectroscopy as a tool inthe study of dye-sensitized solar cells. Inorg. Chim. Acta 361, 729(2008). doi:10.1016/j.ica.2007.05.040

37. P. Docampo et al., Control of solid-state dye-sensitized solar cell performanceby block-copolymer-directed TiO2 synthesis. Adv. Funct. Mater. 20, 1787(2010). doi:10.1002/adfm.200902089

38. J. Bisquert, Chemical capacitance of nanostructured semiconductors: Itsorigin and significance for nanocomposite solar cells. Phys. Chem. Chem.Phys.5, 5360 (2003). doi:10.1039/b310907k

39. L. Kavan, M. Grtzel, Highly efficient semiconducting TiO 2photoelectrodesprepared by aerosol pyrolysis. Electrochim. Acta 40, 643(1995). doi:10.1016/0013-4686(95)90400-W

40. T. Ishihara, J. Takahashi, T. Goto, Optical properties due to electronictransitions in two-dimensional semiconductors (CnH2n+1NH3)2PbI4. Phys.

Rev. B42, 11099 (1990). doi:10.1103/PhysRevB.42.11099Acknowledgments: This work was supported by European Research Council

(ERC) HYPER project no. 279881 and Strategic International ResearchCooperative Program (SCIP) of the Engineering and Physical SciencesResearch Council (EPSRC) and Japan Science and Technology Agency (JST).T.M. thanks the funding program for World-Leading Innovative R&D on

Science and Technology (FIRST Program), Japan, for hybrid solar cellresearch. We thank the NEDO projects for support. M.M.L. is grateful forsupport from the Simms Bursary granted by Merton College, Oxford. Wethank S. K. Pathak for assistance with x-ray diffraction measurements andanalysis. We also thank Agnese Abrusci, James Ball, Pablo Docampo,Andrew Hey, Tomas Leijtens and Nakita Noel, for valuable discussions. TheUniversity of Oxford has filed 3 patents related to this work.

Supplementary Materials

www.sciencemag.org/cgi/content/full/science.1228604/DC1Materials and MethodsSupplementary TextFigs. S1 to S4

9 August 2012; accepted 7 September 2012

Published online 4 October 201210.1126/science.1228604

onOctober

13,

2012

www.sciencemag.org

Downloadedfrom
http://dx.doi.org/10.1103/PhysRevB.59.15374http://dx.doi.org/10.1103/PhysRevB.59.15374http://dx.doi.org/10.1038/369467a0http://dx.doi.org/10.1038/369467a0http://dx.doi.org/10.1021/cm990561thttp://dx.doi.org/10.1021/cm990561thttp://dx.doi.org/10.1063/1.114599http://dx.doi.org/10.1063/1.114599http://dx.doi.org/10.1126/science.286.5441.945http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10542146&dopt=Abstracthttp://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10542146&dopt=Abstracthttp://dx.doi.org/10.1021/ja809598rhttp://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=19366264&dopt=Abstracthttp://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=19366264&dopt=Abstracthttp://dx.doi.org/10.1039/c1nr10867khttp://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=21897986&dopt=Abstracthttp://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=21897986&dopt=Abstracthttp://dx.doi.org/10.1038/nature11067http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=22622574&dopt=Abstracthttp://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=22622574&dopt=Abstracthttp://dx.doi.org/10.1063/1.453467http://dx.doi.org/10.1063/1.453467http://dx.doi.org/10.1021/nn204296bhttp://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=22230653&dopt=Abstracthttp://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=22230653&dopt=Abstracthttp://dx.doi.org/10.1088/0957-4484/19/42/424003http://dx.doi.org/10.1088/0957-4484/19/42/424003http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=21832663&dopt=Abstracthttp://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=21832663&dopt=Abstracthttp://dx.doi.org/10.1002/aenm.201100046http://dx.doi.org/10.1002/aenm.201100046http://dx.doi.org/10.1002/adfm.200900541http://dx.doi.org/10.1002/adfm.200900541http://dx.doi.org/10.1002/adfm.201201223http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=22907987&dopt=Abstracthttp://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=22907987&dopt=Abstracthttp://dx.doi.org/10.1002/pip.1160http://dx.doi.org/10.1002/pip.1160http://dx.doi.org/10.1246/cl.2012.397http://dx.doi.org/10.1246/cl.2012.397http://dx.doi.org/10.1021/j100193a062http://dx.doi.org/10.1021/j100193a062http://dx.doi.org/10.1016/j.ica.2007.05.040http://dx.doi.org/10.1016/j.ica.2007.05.040http://dx.doi.org/10.1002/adfm.200902089http://dx.doi.org/10.1002/adfm.200902089http://dx.doi.org/10.1002/adfm.200902089http://dx.doi.org/10.1039/b310907khttp://dx.doi.org/10.1039/b310907khttp://dx.doi.org/10.1016/0013-4686(95)90400-Whttp://dx.doi.org/10.1016/0013-4686(95)90400-Whttp://dx.doi.org/10.1103/PhysRevB.42.11099http://dx.doi.org/10.1103/PhysRevB.42.11099http://dx.doi.org/10.1103/PhysRevB.42.11099http://dx.doi.org/10.1103/PhysRevB.42.11099http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://www.sciencemag.org/http://dx.doi.org/10.1103/PhysRevB.42.11099http://dx.doi.org/10.1016/0013-4686(95)90400-Whttp://dx.doi.org/10.1039/b310907khttp://dx.doi.org/10.1002/adfm.200902089http://dx.doi.org/10.1016/j.ica.2007.05.040http://dx.doi.org/10.1021/j100193a062http://dx.doi.org/10.1246/cl.2012.397http://dx.doi.org/10.1002/pip.1160http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=22907987&dopt=Abstracthttp://dx.doi.org/10.1002/adfm.201201223http://dx.doi.org/10.1002/adfm.200900541http://dx.doi.org/10.1002/aenm.201100046http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=21832663&dopt=Abstracthttp://dx.doi.org/10.1088/0957-4484/19/42/424003http://dx.doi.org/10.1088/0957-4484/19/42/424003http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=22230653&dopt=Abstracthttp://dx.doi.org/10.1021/nn204296bhttp://dx.doi.org/10.1063/1.453467http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=22622574&dopt=Abstracthttp://dx.doi.org/10.1038/nature11067http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=21897986&dopt=Abstracthttp://dx.doi.org/10.1039/c1nr10867khttp://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=19366264&dopt=Abstracthttp://dx.doi.org/10.1021/ja809598rhttp://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10542146&dopt=Abstracthttp://dx.doi.org/10.1126/science.286.5441.945http://dx.doi.org/10.1063/1.114599http://dx.doi.org/10.1021/cm990561thttp://dx.doi.org/10.1038/369467a0http://dx.doi.org/10.1103/PhysRevB.59.15374


6/12

www.sciencemag.org/cgi/content/full/science.1228604/DC1

Supporting Online Material for

Efficient Hybrid Solar Cells Based on Meso-Superstructured Organometal

Halide Perovskites

Michael M. Lee, Jol Teuscher, Tsutomu Miyasaka, Takurou N. Murakami, Henry J. Snaith*

*To whom correspondence should be addressed. E-mail: [email protected]

Published 4 October 2012 on ScienceExpressDOI: 10.1126/science.1228604

This PDF file includes:

Materials and Methods

Supplementary Text

Figs. S1 to S4


7/12

2

Materials and Methods1

Organometal mixed-halide perovskite synthesis

Methylamine (CH3NH2) solution 33 wt% in absolute ethanol was reacted with hydroiodic acid

(HI) 57 wt % in water with excess methylamine under nitrogen atmosphere in ethanol at room

temperature. Typical quantities were 24 mL methylamine, 10 mL hydroiodic acid and 100 mLethanol. Crystallization of methylammonium iodide (CH3NH3I) was achieved using a rotary

evaporator; a white colored powder was formed indicating successful crystallization.

Methylammonium iodide (CH3NH3I) and lead (II) chloride (PbCl2) was dissolved in anhydrousN,N-Dimethylformamide at a 3:1 molar ratio of CH3NH3I to PbCl2, to produce a mixed halide

perovskite precursor solution. In spin-coated and dried films, the formed perovskite of

methylammonium lead iodide chloride (CH3NH3PbI2Cl) had a final I to Cl ratio of

approximately 2:1 as determined by energy dispersive X-Ray analysis. The excessmethylammonium iodide and chlorine is assumed to be lost via evaporation during the drying

process.

Aluminium oxide paste synthesis

Aluminium oxide dispersion 10 wt% in water was washed by centrifuging at 7500 RPM for 6

hours and redispersing in absolute ethanol with an ultrasonic probe at a duty cycle of 50 % (2seconds on, 2 seconds off) for a duration of 5 minutes. The washing process was repeated for

three cycles. For every 10 g of the original dispersion (1 g total Al2O3) the following was added:

3.33 g of -terpineol and 5 g of a 50:50 mix of ethyl-cellulose 10 cP and 46 cP in ethanol 10 wt

%. After the addition of each component, the mix was stirred for 2 minutes and sonicated withthe aforementioned sonication program for 1 minute. Finally, the resulting mixture was

introduced into a rotary evaporator to remove excess ethanol in order achieve the required paste

consistency suitable for doctor blading, spin-coating or screen-printing.

Perovskite-Sensitized TiO2and Mesoporous-Superstructured Solar Cell fabrication

Fluorine-doped tin oxide (F:SnO2) coated glass (Pilkington TEC 15) 15 /was patterned by

etching with Zn powder and 2 M HCl diluted in milliQ water. The etched substrate was thencleaned with 2% hellmanex diluted in milliQ water, rinsed with milliQ water, acetone and

ethanol and dried with clean dry air. The substrate underwent an oxygen plasma treatment for 5

minutes prior to spray pyrolysis of compact titanium dioxide (TiO2). A thin layer of compactanatase TiO2 of roughly 50 nm in thickness was formed through spray pyrolysis of titanium

diisopropoxide bis(acetylacetonate) diluted in anhydrous ethanol at a volumetric ratio of 1:10

using N2as a carrier gas. Either 0.5 m thick mesoporous Al2O3 layer was deposited by spin-coating Al2O3paste diluted further in anhydrous ethanol at 1:1.5 by weight at 2000 RPM, or 0.5m thick mesoporous TiO2 layer was deposited by spin-coating TiO2paste (Dyesol 18NR-T)

diluted in anhydrous ethanol at 1:2.5 by weight at 2000 RPM. The layers were then sintered in

air at 550 C for 30 minutes. Once cooled and cut down to device size 25 l of 20 wt%perovskite precursor solution was dispensed onto each pre-prepared mesoporous electrode film

spin-coating at 1500 RPM for 30 seconds in air. The coated films were then placed on a hotplate set at 100 C for 45 minutes in air. During the drying procedure at 100 C, the coated

electrode changed color from light yellow to dark brown, indicating the formation of the

1Unless stated otherwise all chemicals were purchased from Sigma-Aldrich and were anhydrous if available.


8/12

3

perovskite film. 25 l of a chlorobenzene solution containing 68 mM Spiro-OMeTAD, 55 mMtert-butylpyridine and 9 mM lithium bis(trifluoromethylsyfonyl)imide salt was cast onto the

perovskite coated substrate and spun at a rate of 2000 RPM for 45 seconds. Cells were left in the

dark in air overnight prior to thermal evaporation of 200 nm Ag electrodes to complete the solarcells.

Solar Cell Characterization

Current-Voltage characteristics were measured (2400 Series SourceMeter, Keithley

Instruments) under simulated AM 1.5G sunlight at 100 mWcm-2

irradiance; generated using anAAB ABET technologies Sun 2000 solar simulator and calibrated using an NREL calibrated

silicon reference cell with a KG5 filter to minimise spectral mismatch (the mismatch factor was

calculated to be less than 1%). The solar cells were masked with a metal aperture to define theactive area which was typically 0.09 cm

2 and measured in a light-tight sample holder to

minimize any edge effects.

Photovoltaic action spectra were measured (2400 Series SourceMeter, Keithley Instruments)with chopped monochromatic light incident which were biased with white light-emitting diodes

(LED) at an equivalent solar irradiance of 10 mWcm-2

. The monochromatic light intensity for

the incident photon-to-electron conversion efficiency (IPCE) was calibrated with a UV-enhancedsilicon photodiode. The solar cells were masked with a metal aperture to define the active area

which was typically 0.09 cm2and measured in a light-tight sample holder to minimize any edge

effects.

Photo-induced absorption (PIA) spectra were obtained from perovskite/TiO2 or Al2O3 films

deposited on FTO coated glass. The films were excited with an Argon ion laser tuned at 496.5nm with a maximum fluence of 50 mW cm-2

and chopped at a frequency of 23 Hz. The detectionis made with a continuous white light probe (halogen bulb) of around 1 sun intensity onto the

sample. After passing through the sample, the probe beam enters a monochromator (SpectraPro-

2300i, Acton Research Corporation) coupled to diode for detection in the visible (PDA10A,Thorlabs) and in the NIR (ID-441-C, Acton Research Corporation). Acquisition is made by a

lock in amplifier locked at the light modulation frequency (SR830, Stanford Research Systems)

and a NI USB-6008 (National Instruments) acquisition card. A computer running LabView(National Instruments) controls the setup and record spectra. No further treatment is applied to

the data.


9/12

4

SOM Text

Determining the presence of mixed-halide perovskite in mesoporous Al2O3

To confirm the presence of the CH3NH3PbI2Cl throughout the mesoporous Al2O3, we haveperformed energy dispersive x-ray (EDX) analysis on a cross section of a device. Fig. S2 shows

a cross-sectional scanning electron micrograph (SEM) of a ~3 m thick device (left), and

energy-dispersive x-ray (EDX) spectroscopy with elemental mapping of (right) aluminium, lead,

chlorine, iodine. We show the uniform distribution of Al, Pb, Cl, and I throughout a ~3 m thickfilm. We note that for the optimized devices the mesoporous alumina films are only ~0.5 m

thick, but we have used a 3 m due to spatial resolution plimitations of the EDX technique. The

elemental composition determined by the EDX gives an approximately 2:1 I:Cl ratio.

Comparison between sensitised versus meso-superstructure device architecturesFig. S3 shows histogram plots of key solar cell performance parameters: fill factor, open-circuit

voltage, short-circuit current and photo-conversion efficiency for a large batch of perovskite cellsmeasured under simulated AM 1.5 100 mW cm-2

illumination. The main observation is that the

fill factor is generally lower but the open-circuit voltage is significantly higher, giving overall aslightly higher efficiency for the meso-superstructure solar cells (MSSC) as compared to the

TiO2sensitized devices. The distribution is reasonably wide, reducing this spread in performance

is central to the commercialization of this technology.

Confirming the insulating nature of Al2O3To confirm the insulating nature of alumina (Al2O3), solid-state dye-sensitized solar cells were

made with either mesoporous titania (TiO2) or mesoporous alumina (Al2O3). Fig. S4 Current-

voltage characteristics under AM 1.5 (100 mWcm-2

) simulated sunlight (solid) and in dark(dashed) to red trace- TiO

2, and bottom black trace- Al

2O

3. The devices were constructed in the

same manner as the perovskite-sensitized or the meso-superstructured solar cells (using spiro-

OMeTAD as the hole-transporing medium); however, a prototypical ruthenium based dye

(termed N719) was used in lieu of the perovskite absorber. The film thicknesses of themesoporous TiO2and Al2O3were around 500nm, accounting for the relatively low photocurrent

of the TiO2sensitized device.


10/12

5

Figures

Fig. S1. X-ray Diffraction (XRD) spectra of CH3NH3PbI2Cl spin-coated on a glass slideand heated to 100C before measuring.

Fig. S2. Cross-sectional scanning electron micrograph (SEM) of a ~3 m thick device(left), andenergy-dispersive x-ray (EDX) spectroscopy with elemental mapping of (right)aluminium, lead, chlorine, iodine.


11/12

6

Fig. S3.Histogram plots of solar cell performance parameters: open-circuit voltage

(VOC), short-circuit current (JSC) fill factor (FF) and photo-conversion efficiency () for alarge batch of CH3NH3PbI2Cl sensitized TiO2photovoltaic devices (black, total of 262devices) and meso-superstructured solar cells (Al2O3based) (red, total of 767 devices).The Gaussian fits have been added to aid the eye.


12/12

7

Fig. S4. Current-voltage characteristics measured under AM 1.5 100mWcm-2simulatedsunlight (solid) and in dark (dashed) for solid-state dye-sensitised solar cells with TiO2(red trace with crosses) and Al2O3. (black trace with circles).

Documents

2012 Henry Efficient Hybrid Solar Cells Based On