Study on the effects of polymer donor aggregation on all-polymer and non-fullerene small molecule-polymer solar cells

Abstract

To enhance the efficiency and stability of polymer solar cells, the research to modify and observe the characteristics of various acceptors has been conducted consistently. However, there is a few research for polymer donors ($P_Ds$) which needs more attention to utilize the adequate $P_D$ for various type of acceptors including polymer acceptor ($P_A$), non-fullerene small molecule acceptor (NFSMA), and fullerene. Here, the aggregation behaviors of $P_Ds$ were investigated according to two different system with $P_A$ and NFSMA. The strong aggregation behavior could affect the blend morphology and electrical properties as photovoltaic devices. For all-PSCs, the hugely aggregated $P_D$ led to severe phase separation and low short-circuit current density ($J_{sc}$) of device performance. In contrast, well-mixed but adequate charge pathway was obtained with aggregated $P_D$ blended with NFSMA, which induced the high $J_{sc}$ and charge mobility. The comprehensive understanding the effect of aggregated $P_D$ could shorten the cost to design the best system of polymer solar cells.