Fluorinated benzotriazole-modified random terpolymer acceptors towards less thickness-sensitive all-polymer solar cells

Naphthalene diimide (NDI)-based n-type polymers have been reported as the most widely employed polymer acceptors so far. However, all-polymer solar cells (all-PSCs) based on NDI-typed acceptors commonly suffer from low short-circuit current density (Jsc) due to the deficient absorption coefficients of polymer acceptors and unsatisfactory morphologies. In this work, based on the most widely used copolymer acceptor N2200, we designed terpolymer acceptors named PNDI-BTzx (x = 5 and 10) by randomly embedding a certain amount of fluorinated benzotriazole (2f-BTz) into N2200 backbone. The enhanced absorption coefficients, relatively weakened polymer crystallinities and improved polymer miscibility were obtained from terpolymer acceptors compared to N2200. Synchronously benefited from improved absorption and optimized morphology, all-PSCs based on PNDI-BTz5 demonstrated enhanced photovoltaic performance with power conversion efficiency (PCE) and Jsc of 6.72% and 12.54 mA cm−2 than 5.67% and 10.80 mA cm−2 from N2200-control. In addition, satisfactory reproducibility was obtained with comparable performance among different batches of PNDI-BTzx (x = 5 and 10). And more interestingly, all-PSCs based on PNDI-BTz5 possessed better thickness tolerance than N2200. These results offered useful guidelines to realize reproducible-performance and thick-film practical all-polymer photovoltaic applications through designing random terpolymer acceptors. Enhanced absorption coefficient and improved miscibility were synchronously achieved by incorporating certain amount of 2f-BTz unit into N2200 backbone, resulted in boosted photovoltaic performance, optimized blend morphology, satisfactory batch reproducibility and better thickness tolerance. [Display omitted] •Improved photovoltaic performance was obtained from fluorinated benzotriazole-embedded N2200-based terpolymer.•Terpolymers possessed enhanced absorption coefficients and improved polymer miscibility.•Devices based on terpolymer demonstrated satisfactory batch-to-batch reproducibility.•Less sensitivity to active layer thickness was achieved in terpolymer-based all-PSCs.