Efficiency Enhancement of Polymer Solar Cells Based on Poly(3-hexylthiophene)/Indene-C70 Bisadduct via Methylthiophene Additive

Photovoltaic performance of polymer solar cells based on poly(3-hexylthiophene) (P3HT) as the donor and indene-C70 bisadduct (IC70BA) as the acceptor is improved by adding 3 vol% 3-methylthiophene (MT) or 3-hexylthiophene (HT) as processing additives. The results of UV-vis absorption spectroscopy, X-ray diffraction analysis and atomic force microscopy indicate that with the MT or HT processing additive, the active layer of the blend of P3HT/IC70BA showed strengthened absorbance, enhanced crystallinity and improved film morphology. The power conversion efficiency (PCE) of the PSCs was improved from 5.80% for the device without the additive to 6.35% for the device with HT additive and to 6.69% with MT additive. The PCE of 6.69% is the top value reported so far for the PSCs based on P3HT.