Poly[2,5-bis(2-decyldodecyl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione-(E)-1,2-di(2,2’-bithiophen-5-yl) ethene] (PDPPDBTE) was successfully incorporated as a p-type hole transporting material in solid-state organic-inorganic hybrid solar cells. The excellent optical and electrical properties of organo-lead halide perovskite (CH3NH3PbI3) nanocrystals used as a light harvester yielded a 9.2% power conversion efficiency (PCE) for the best-performing cell that exceeded the value (7.6%) obtained from the best hole conductor yet reported (2,2',7,7'-tetrakis(N,N-di-p-methoxyphenyl-amine)9,9'-spirobifluorene, spiro-MeOTAD). The high PCE was attributed to the optimal oxidation potential (5.4 eV) and excellent charge carrier mobility of the polymer. The hydrophobicity of the polymer prevented water permeation into the porous perovskite heterojunction, and long-term aging tests over 1000 hours confirmed the enhanced stability of the PDPPDBTE-based cells.
Figure 1. (a) D-π-A conjugated polymer successfully incorporated with perovskite-based organic-inorganic hybrid solar cells, outperforming the ever-best spiro-MeOTAD hole transporting material. (b) J-V curves of the hybrid solar cells made from spiro-MeOTAD, P3HT, and PDPPDBTE HTMs. (c) The effective conductivities of the HTMs ((A): including Li-TFSI and tBP additives).