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  • International Conference of Solution Processed Semiconductor Solar Cells - Oxford 2014

    International Conference of Solution Processed Semiconductor Solar Cells, Oxford, United Kingdom, 10th to 12 th September 2014

    edited by

    Henry Snaith

    Department of Physics, University of Oxford, United Kingdom

    You are invited to participate in the International Conference Solution processed Semiconductor Solar Cells, which will be held from 10 to 12 September 2014, in Oxford, United Kingdom.

    The Solution Processed Semiconductor Solar Cell 2014 conference will bring together leading scientists with expertise in both inorganic and organic solar cells, who have brought their skills to bear upon hybrid and inorganic solution processed photovolatics. Specifically focused technologies are, semiconductor sensitized, solution processed thin film such as CZTS, quantum dot solar cells and newly emerged perovskite solar cells. We expect a significant fraction of the conference will be dedicated to perovskite solar cells, but strongly encourage submission of abstracts for the other device types, since we want to encourage fruitful cross fertilization from between the fields.

    Topics include but are not limited to, new materials synthesis and characterisation, fundamental understanding through spectroscopic and optoelectronic investigations, photonic and plasmonic control and enhancement, device optimisation and long term stability investigations. We warmly invite you to submit contributing abstracts to what promises to be an enlightening conference.

    International Conference of Solution Processed Semiconductor Solar Cells (SSSC14)

    Oxford, United Kingdom

    Scientific Committee

    Henry Snaith Iván Mora-Seró Sam Stranks

    Department of Physics, University of Oxford, United Kingdom University Jaume I, Spain Department of Physics, University of Oxford, United Kingdom

    International Conference of Solution Processed Semiconductor Solar Cells (SSSC14)

    Oxford, United Kingdom

    Invited Speakers

    Juan Bisquert Universitat Jaume I, Spain Lioz Etgar The Hebrew University of Jerusalem, Israel Feliciano Giustino University of Oxford, United Kingdom Gary Hodes Weizmann Institute of Science, Israel Seigo Ito University of Hyogo, Japan Alex Jen University of Washington, United States Mercouri Kanatzidis Northwestern University, United States Gerasimos Konstantatos ICFO, Spain David Mitzi Tsutomu Miyasaka

    Duke University, USA Toin University of Yokohama, Japan

    Arthur Nozik National Renewable Energy Laboratory, United States Emilio Palomares Institute of Chemical Research of Catalonia, Spain Nam-Gyu Park Sungkyunkwan University, Korea Annamaria Petrozza Center for Nanoscience and Technology, Italy Yang Yang University of California, United States Arie Zaban Bar-Ilan University, Israel

  • International Conference of Solution Processed Semiconductor Solar Cells - Oxford 2014

    Thursday 11th September 8.40 - 9.10 Development of High-Performance Solution-Processed Chalcopyrite/Kesterite Films for Photovoltaic Application

    David Mitzi IBM TJ Watson Research Center, PO Box 218 10598 Yorktown Heights, New York

    Thursday 11 th

    September 9.40 - 10.10 Unique Quantization Effects in Quantum Dots and Quantum Dot Solar Cells for PV and Solar Fuels

    Arthur Nozik a, b

    , Matt Beard b , Joey Luther

    b , Mark Hanna

    b , Justin Johnson

    b , Octavi Semonin

    b

    a, University of Colorado, Boulder, 215 UCB University of Colorado, Boulder, 00309, US b, NREL, 1617 Cole Blvd, Golden, 80409, US

    In quantum dots (QDs), quantum rods (QRs) and unique molecular chromophores that undergo singlet fission (SF) the relaxation pathways of photoexcited states can be modified to produce efficient multiple exciton generation (MEG) from single photons . We have observed efficient MEG in PbSe, PbS, PbTe, and Si QDs and efficient SF in molecules that satisfy specific requirements for their excited state energy levels. We have studied MEG in close-packed QD arrays where the QDs are electronically coupled in the films and thus exhibit good transport while still maintaining quantization and MEG. We have developed simple, all-inorganic QD solar cells that produce large short-circuit photocurrents and respectable power conversion efficiencies via both nanocrystalline Schottky junctions and nanocrystalline p-n junctions. These solar cells also showed for the first time external quantum yields (QYs) for photocurrent that exceed 100% in the photon energy regions of the solar spectrum where MEG is possible (i.e., energy conservation is satisfied); the photocurrent internal QYs from MEG as a function of photon energy match those determined via time-resolved spectroscopy and the results settle controversy concerning MEG. Recent analyses of the dramatic effects of solar concentration combined with MEG on the conversion efficiency of solar cells will also be discussed. The properties required for nanocrystals and SF molecules to achieve the high solar conversion efficiencies predicted by theory will be presented. Regarding production of solar fuels, all viable systems must have the following features: two photosystems arranged either in a Z-scheme analogous to biological photosynthesis, or two tandem p-n junctions connected in series where sufficient photopotential (1.23 V + overvoltage for H2O splitting) is generated to drive the redox reactions; strong absorption of solar photons; efficient separation of the photogenerated e-h pairs, efficient transport to and collection of the separated carriers at electrocatalytic surfaces; low overvoltages; appropriate alignment of the redox potentials in the photoelectrodes with those of the fuel-producing reactions; and resistance to dark-and photo- corrosion achieving long-term photostability. Cells with buried junctions in a tandem p-n configuration or a Z-scheme can achieve these requirements.

    Thursday 11 th

    September 10.10 - 10.25 Reversible Photo-induced Halide Segregation in Mixed-halide Hybrid Perovskites for Photovoltaics

    Eric Hoke a , Eva Unger

    a , Hemamala Karunadasa

    b , Michael McGehee

    a

    a, Material Science and Engineering, Stanford University, 476 Lomita Mall, Stanford, CA, 94305, US b, Chemistry, Stanford University, 333 Campus Dr, Stanford, CA 94305, US

    Mixed-halide hybrid perovskites such as CH3NH3Pb(BrxI1-x)3 are a promising family of photovoltaic absorber materials that have achieved power conversion efficiencies of over 17%. By varying the halide composition, the optical bandgap can be tuned over the range 1.6-2.3 eV, making this family of materials a suitable candidate for both single-junction solar cells as well as the large bandgap absorber of a tandem solar cell. However, reports of mixed CH3NH3Pb(BrxI1-x)3 devices with higher bromine content have so far not been able to achieve the increase in open circuit voltage that may be expected from the larger bandgap of these materials. We observe photo-induced halide segregation in bromine- rich (0.2

  • International Conference of Solution Processed Semiconductor Solar Cells - Oxford 2014

    dependence to the hysteretic behavior in planar CH3NH3PbI3-xClx solar cells which is suggestive of a prominent role of halide migration in perovskite photovoltaic hysteresis. These observations are reminiscent of photo-initiated halide migration in lead halides and other metal halides, which has been proposed to occur via a halide-vacancy diffusion mechanism from surface sites. This suggests that improved control of the perovskite stoichiometry, crystallinity and surface passivation are potential strategies towards reducing halide migratory effects and improving the stability of halide perovskite optoelectronic devices.

    Thursday 11 th

    September 10.25 - 10.40 Optical Properties of Perovskite-Based Solar Cells

    James Ball a , Maximilian Hoerantner

    b , Samuel Stranks

    b , Sven Huettner

    c , Mingzhen Liu

    b , Wei Zhang

    b ,

    Ullrich Steiner c , Henry Snaith

    b

    a, Istituto Italiano di Italiano, Centre for Nanoscience and Tecnology, Via Giovanni Pascoli 70/3, Milano, 20133, IT b, University of Oxford, Clarendon Laboratory, Parks Road, Oxford, OX1 3PU, UK c, University of Cambridge, Cavendish Laboratory, JJ Thomson Avenue, Cambridge, CB3 0HE, UK

    Perovskite light-harvesters have rapidly emerged to the forefront of photovoltaics research exhibiting high power-conversion efficiencies and the promise of low-cost fabrication in devices. Despite recent progress in describing the internal mechanisms for photocurrent generation in perovskite solar cells, a full understanding of the device operation still requires an optical analysis of the device stack. This provides an additional platform for maximising the power-conversion efficiency through a precise determination of parasitic losses caused by optical coherence and absorption in non-photoactive layers. Here we present a transfer-matrix model for the charge-generation profile under sunlight in state-of- the-art perovskite-based planar-heterojunction solar cells using experimental refractive index data from spectroscopic ellipsometry. Excellent agreement between the model and experiment is obtained and reveals some important features of the device operation. In particular, we find the optimum thickness for photocurrent generation, an accurate derivation of the wavelength dependence of the internal quantum efficiency from the external quantum efficiency, and the dependence of the photocurrent on incidence angl