Cyanobenzene-modified polymer acceptors for high-efficiency all-polymer solar cells with low energy loss

Abstract

Despite the remarkable advancements witnessed recently in all-polymer solar cells (all-PSCs), simultaneously achieving improvement of open-circuit voltage (VOC) and short-circuit current density (JSC) through rational molecular design is still extremely challenging. Herein, we present the design and synthesis of two novel polymer acceptors, P-phCN and P-BphCN, to precisely manipulate optical absorption and electronic properties by introducing asymmetric and symmetric cyanobenzenes. Compared with symmetric cyanobenzene-modified P-BphCN, the asymmetric cyanobenzene-modified P-phCN-based blend films possess a more homogeneous fibril network morphology with suitable phase separation and tighter face-on stacking, which can promote charge generation, extraction and more balanced charge mobilities in corresponding all-PSCs. Thus, P-phCN-based all-PSCs not only achieve optimized JSC (24.47 mA cm⁻²) and VOC (0.946 V), but also exhibit a relatively low energy loss of 0.518 eV. Consequently, P-phCN-based devices achieve a higher power conversion efficiency (PCE) of 17.10% in binary all-PSCs. This work demonstrates that the use of cyanobenzene to modify the polymer acceptor central core is a simple and effective strategy, which provides new opportunities to achieve high performance all-PSCs with small energy loss.