The improved performance in the ternary bulk heterojunction solar cells

The ternary blend films have been fabricated via adding 4,4′-N,N′-dicarbazole-biphenyl (CBP, a hole transport material widely used in organic light emitting diodes) into the poly(3-hexylthiophene):[6,6]-phenyl C61-butyric acid methyl ester (P3HT: PCBM). Despite the wide bandgap (3.1 eV) of the CBP, the solar cell utilizing the optimized P3HT:PCBM:CBP blend film showed an increase of 16% in power conversion efficiency and 25% in short-circuit current than the compared standard P3HT:PCBM blend film. This is attributed to the fact that the addition of the CBP could enhance the aggregation of the P3HT chains and thereby reduce the hole-electron recombination at the interface of P3HT and PCBM. We provide a simple, effective way to improve the performance of P3HT based bulk heterojunction solar cells.