Energy level tuning of ‘Z’-shaped small molecular non-fullerene electron acceptors based on a dipyrrolo[2,3-b:2′,3′-e]pyrazine-2,6(1H,5H)-dione acceptor unit for organic photovoltaic applications: a joint experimental and DFT investigation on the effect of fluorination

Abstract

Three dipyrrolo[2,3-b:2′,3′-e]pyrazine-2,6(1H,5H)-dione based small molecule non-fullerene acceptors with various end-capped fluorine units have been investigated.