p–π Conjugated Polymers Based on Stable Triarylborane with n-Type Behavior in Optoelectronic Devices

Abstract

p–π conjugation with embedded heteroatoms offers unique opportunities to tune the electronic structure of conjugated polymers. An approach is presented to form highly electron-deficient p–π conjugated polymers based on triarylboranes, demonstrate their n-type behavior, and explore device applications. By combining alternating [2,4,6-tris(trifluoromethyl)phenyl]di(thien-2-yl)borane (FBDT) and electron-deficient isoindigo (IID)/pyridine-flanked diketopyrrolopyrrole (DPPPy) units, we achieve low-lying lowest unoccupied molecular orbital (LUMO) and highest occupied molecular orbital (HOMO) energy levels, high electron mobilities, and broad absorptions in the visible region. All-polymer solar cells with these polymers as electron acceptors exhibit encouraging photovoltaic performance with power conversion efficiencies of up to 2.83 %. These results unambiguously prove the n-type behavior and demonstrate the photovoltaic applications of p–π conjugated polymers based on triarylborane.