The halogen effect of perylene diimide-based non-fullerene acceptors on photovoltaic properties

Abstract

To develop photovoltaic materials based on perylene diimide, two non-fullerene acceptors namely PCPD-F and PCPD-Cl are rationally designed and readily synthesized. By introducing the cyclopentadithiophene unit with the strong electron-donating ability, PCPD-F and PCPD-Cl exhibit strong and bathochromic absorption compared to other perylene diimide derivatives. Meanwhile, different halogens in PCPD-F and PCPD-Cl significantly affect the physicochemical properties and device performance. With the substitution of chlorine atom, PCPD-Cl shows relatively broad absorption and strong crystallinity. However, the chlorination makes PCPD-Cl less miscible with polymer donors, leading to the unfavorable morphology with large-scale phase separation in organic solar cells. Consequently, the device based on PCPD-F achieves the best power conversion efficiency of 9.03% by blending with the polymer donor PM6, which is among the high-performance organic solar cells based on perylene diimide. This work demonstrates it is crucial to meticulously select the substituted atom and position in the design of non-fullerene acceptors.