Roles of solvent additive in organic photovoltaic cells through intensity dependence of current-voltage characteristics and charge recombination

摘要

In this research, the enhanced power conversion efficiency of PBnDT-FTAZ:PC_(70)BM bulkheterojunction (BHJ) solar cells (over 7%), fabricated with a solvent additive (1,8-diiodooctane, 3%), was demonstrated. The appropriate ratio of solvent additive leads to a device with increased J_(SC), fill factor, and favorably controlled nanomorphology phase separation. Furthermore, the device with BHJ film fabricated with the solvent additive exhibited improved charge collection and simultaneously reduced charge recombination from a systematic light intensity analysis. The lack of Shockley-Read-Hall recombination at open circuit, the dominance of bimolecular recombination only when approaching open circuit, and an improved charge collection probability (95.5%) at short circuit contribute to high performance organic photovoltaic cells.