Making Solar CellsD. Venkataraman (DV)

Department of ChemistryUmass Amherst

dv@chem.umass.eduJune 29, 2010

Efficiency of Photovoltaic Cells Depend on Absorption in the Solar Spectrum Charge SeparationCharge MobilityCharge Collection

Photovoltaic Cells

Exciton

Active Material

Source: National Renewable Energy Laboratory

Organic Photovoltaic Devices StabilityEfficiency

Cost

End-User Application

Konarka KonarkaHome Depot/BP Solar

What is the Problem?

Si or III-V Cells

Exciton diffusion distance >100 nm

Excitons loosely bound

Organic/Hybrid/Dye-sensitized

Exciton diffusion distance <10 nm

Excitons tightly bound (Frenkel Excitons)

Low dielectric constant

10 nm

Gregg, B. A., Excitonic solar cells. Journal of Physical Chemistry B 2003, 107 (20), 4688-4698.

Active Material-conjugated molecules

/polymers

StabilityEfficiency Cost

Active LayerMorphologies

Electrode/Active Layer Interfaces

Device Fabrication/Encapsulation

Intrinsic

Extrinsic

OMe

O

PCBM – [6,6]-phenyl-C61-butyric acid methyl ester

SH

C6H13

SS

C6H13

C6H13

Hm

Poly(3-hexylthiophene) (P3HT)

Organic Photovoltaic Cells

Bulk Heterojunction CellsEfficiency ~ 5%

Padinger, F.; Rittberger, R. S.; Sariciftci, N. S., Effects of postproduction treatment on plastic solar cells.Advanced Functional Materials 2003, 13 (1), 85-88. Ma, W. L.; Yang, C. Y.; Gong, X.; Lee, K.; Heeger, A. J. "Thermally stable, efficient polymer solar cells with nanoscale control of the interpenetrating network morphology," Advanced Functional Materials 2005, 15, 1617-1622.

100 nm