Favorable electron extraction from non-fullerene photoactive layers enabled by tetrakisarylamine-functionalized ethylenediamines in polymer solar cells

Abstract

Engineering the cathode interface of polymer solar cells plays a critical role in mitigating defects and charge recombination, thereby improving device efficiency. Herein, we report the development of two novel tetrakisarylamine-functionalized ethylenediamines (TAAs) as cathode interlayers in organic bulk-heterojunction solar cells based on a non-fullerene BTP-4Cl acceptor and a PCE14 polymer donor. These tetrakisaryldiamines, which are easily synthesized from ethylene diamine and readily processable with common organic solvents, exhibit extended π-conjugation through vinyl linkers. The incorporation of TAAs on the top of the zinc oxide effectively alters the contact between the photoactive layer and the oxide, minimizing interfacial traps and enhancing charge transfer, as revealed by lower series and higher shunt resistances. The TAA with carbazole units at the end of the four arms shows the greatest increase in the performance of non-fullerene organic solar cells and increases the power conversion efficiency from 14.1% to 15.1%. TAAs also enhance long-term stability during device storage because of the effective modification of the cathode contact. Tetrakisarylamine-functionalized ethylenediamines (TAAs), used as an electron-transporting interlayer, modify the contact between the photoactive PCE14:BTP-4Cl layer and the ZnO-based cathode, thereby reducing interfacial trap states, facilitating charge transfer, and ultimately improving both power conversion efficiency and device stability.