Effect of processing additive on morphology and charge extraction in bulk-heterojunction solar cells

Abstract

The effects of the 1,8-diiodooctane (DIO) processing additive on the nanomorphology, charge generation, and charge transport in the PBnDT-FTAZ/PC₇₀BM BHJ solar cells are demonstrated. The optimized nanoscale donor–acceptor morphology is achieved with 3% DIO processing additive in the BHJ film. The BHJ film with 3% DIO exhibits efficient charge generation as indicated by the decreased PL and the associated lifetime compared to the BHJ film without DIO. The balanced charge transport decreased series resistance and balanced hole and electron mobility is also observed in the device fabricated with 3% DIO. Because of the efficient charge extraction, J_SC and PCE of the devices are increased from 3.7 mA cm⁻² and 1.9% to 13.7 mA cm⁻² and 7%, respectively. In summary, optimized fabrication with DIO as a processing additive improves the morphology, faster charge generation, and balanced charge transport in the PBnDT-FTAZ:PC₇₀BM BHJ film, which leads to high performance BHJ solar cells.