Efficient flexible and thermally stable pentacene/C60 small molecule based organic solar cells

Flexible thin film solar cells based on a pentacene/${\mathrm{C}}_{60}$ heterojunction on indium tin oxide coated polyethylene terephthalate (PET) substrates are described. Devices grown on PET are compared to those on glass substrates. The nature of the organic grains grown on PET and glass substrates is shown to have a significant impact on the device short circuit current. Device performance under mechanical strain and elevated temperature is reported. Devices deliver an $8.8\mathrm{mA}{\mathrm{cm}}^{-2}$ short circuit current density with a 1.6% power conversion efficiency under an AM1.5 simulated solar intensity of $80\mathrm{mW}{\mathrm{cm}}^{-2}$ . The relatively low $300\mathrm{mV}$ open circuit voltage appears to limit device efficiency.