A Facile Method of Solvent-Flushing to Building Component Distribution within Photoactive Layer for High Performance Organic Solar Cells.

Suitable donor and acceptor distribution in the blended photoactive layer benefits for the charge transfer and exciton separation to boost the performance of organic solar cells (OSCs). Herein, we propose a universal method of solvent-flushing to building component distribution in photoactive layer based on the different solubility of the donor and acceptor in acetylacetone (Acac). The donor and acceptor concentration distribution through the photoactive layers is investigated by the time-of-flight secondary-ion mass spectroscopy (TOF-SIMS), and the surface concentration changes are examined by contact angle measurements and atomic force microscopy (AFM) tests. The charge transfer properties of OSCs before and after Acac flushing are further investigated by the rectification ratio and light intensity dependent Jsc and Voc measurements. For inverted OSCs based on PBDB-TF:IT-4F, the power conversion efficiency (PCE) enhances from 12.87% to 14.05%, and for PBDB-TF:Y6 based device, the PCE also significantly increases from 15.40% to 16.51%, due to greatly enhanced Jsc and FF, benefited from enhanced charge transport and suppressed charge recombination by solvent flushing. Our findings suggest that solvent-flushing is a simply-processed and easily-controlled method to achieve vertical component distribution in photoactive layer to boost the performance of OSCs.