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Organic Solar Cells

Organic Solar Cells. Elizabeth Thomsen. Organic Semiconductors. Organic. Semi Conductor. Artist’s impression!. Organic Semiconductors. Combine the virtues of plastics with those of semiconductors High optical absorption coefficients Properties tuned with flexible synthesis

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Organic Solar Cells

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  1. Organic Solar Cells Elizabeth Thomsen

  2. Organic Semiconductors Organic Semi Conductor Artist’s impression!

  3. Organic Semiconductors • Combine the virtues of plastics with those of semiconductors • High optical absorption coefficients • Properties tuned with flexible synthesis • Low cost fabrication

  4. Organic Solar Cells • Potential for medium efficiency, very low cost solar cells

  5. Organic Solar Cells Charge extraction of carriers Absorption of photons to form excitons Charge separation of excitons

  6. 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

  7. Active Layer Materials Electron transporter Hole transporter Conjugated polymer Fullerenes Conjugated dendrimer/ small molecule Nanocrystals

  8. 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

  9. Conjugated small molecule: nanocrystal composite Oligomer Dendrimer PbS CdS Sulphur flakes in toluene Toluene DMSO Oligomer: CdS in chloro-benzene OligomerCadmium acetate 110°C

  10. Oligomer: CdS

  11. CdS Rods

  12. 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

  13. Acknowledgements • Alexandros Stravinadis • Andrew Watt Thankyou for listening!

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