Metallated terpolymer donors with strongly absorbing iridium complex enables polymer solar cells with 16.71% efficiency

Abstract

With the sharp growth of non-fullerene acceptors, it is still challenging to develop new polymer donors for highly efficient polymer solar cells (PSCs). Here, a series of metallated terpolymer donors PM6Irx (x = 1%, 3%, 5%) are synthesized by incorporating a new iridium complex, named M1, into the backbone of the state-of-the-art polymer PM6. The M1 shows a strong absorption in the visible region, which is beneficial to enhance photon harvesting in the active layer. The PM6Ir1:Y6 based PSCs exhibit the best power conversion efficiency (PCE) of 16.71% with short-circuit current density (JSC) of 26.16 mA cm-2, open-circuit voltage (VOC) of 0.848 V and fill factor (FF) of 75.33%. A PCE improvement of about 7% is achieved compared with PM6Ir0:Y6 based control device with PCE of 15.65%, which is due to the markedly increased JSC and FF. The introduction of a moderate amount of M1 enhances the photon harvesting, triplet excitons and lifetime, charge mobility as well as optimizes the active layer morphology. This work indicates that iridium complexes with strong absorption in the visible region have a great potential to promote the photovoltaic performance.