A polymer acceptor containing the B←N unitfor all-polymer solar cells with 14% efficiency

Abstract

The development of all polymer solar cells (all-PSCs) is limited by the lack of polymer acceptors. An effective strategy to design high-efficiency polymer acceptors is to copolymerize small molecular acceptors with electron-rich linking units. In this work, we develop a new polymer acceptor by copolymerizing a small molecular acceptor with an electron-deficient linking unit based on the boron–nitrogen coordination bond (B←N). The incorporation of B←N into the polymer acceptor downshifts the LUMO/HOMO energy levels of the polymer by ca. 0.1 eV, and thus facilitates photo-induced hole transfer from the polymer acceptor to polymer donor. The all-PSC device based on the polymer acceptor containing B←N exhibits a power conversion efficiency (PCE) of 14.3%, which is much higher than that of the control polymer acceptor without B←N (PCE = 7.2%). This is attributed to the improved phase separation morphology and the facilitated photo-induced hole transfer of the active layer based on the polymer acceptor containing B←N. These results suggest that B←N based building blocks with electron-deficient properties are promising to design high-performance polymer acceptors.