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Organic Solar Cells
Elizabeth Thomsen
Organic Semiconductors
Artist’s impression!
Semi Conductor
Organic
Organic Semiconductors
Combine the virtues of plastics with those of semiconductors
High optical absorption coefficients
Properties tuned with flexible synthesis
Low cost fabrication
Organic Solar Cells
Potential for medium efficiency, very low cost solar cells
Organic Solar Cells
Absorption of photons to form excitons
Charge separation of excitons
Charge extraction of carriers
Conjugated materials Polymers generally
insulating Alternating single and
double bonds (conjugated) π electrons able to
delocalise into clouds above and below the chain
Bandgap suitable for absorption of sunlight
Active Layer Materials
Hole transporter
Electron transporter
Conjugated polymer
Conjugated dendrimer/
small molecule
Fullerenes
Nanocrystals
Conjugated material: nanocrystal composites Typically nanocrystals synthesised separately to
polymer, then mixed Disadvantages
Nanocrystal surfactant inhibits charge transfer Co-solvents required for mixing: can adversely affect
nanocrystal solubility and polymer chain orientation One-pot synthesis of conjugated polymer:
nanocrystal composite developed by Watt et al. Extended this synthesis to a conjugated oligomer
and a dendrimer
Conjugated small molecule: nanocrystal composite
OligomerCadmium acetate
Toluene DMSO
110°C
Sulphur flakes in toluene Oligomer:
CdS in chloro-benzene
Dendrimer
Oligomer
PbS CdS
Oligomer: CdS
CdS Rods
Final thoughts
Grew PbS and CdS nanocrystals in oligomer, PbS nanocrystals in dendrimer
Highly likely the synthesis can be generalised to a variety of conjugated soluble small molecule: nanocrystal systems
Combination of materials extends the absorption spectrum
Direct interaction between the small molecule and the nanocrystal is likely to enable efficient charge separation
Shape control of nanoparticles may improve charge transfer through the device
Acknowledgements
Alexandros Stravinadis Andrew Watt
Thankyou for listening!
