Theoretical studies of new iridium-based terpolymer donors for high-efficiency triplet-material-based organic photovoltaics: Incorporation of different iridium(III) complexes

Screening potential terpolymer donors for high-performance triplet-material-based organic photovoltaics (T-OPVs) has been a challenge. Herein, four terpolymer donors, with different bis-tridentate iridium(III) complexes incorporated into the backbone of PTB7Ir, were designed and investigated by DFT and TD-DFT methods. The results show that, for designed 1–4 molecules, the bis-tridentate architecture in iridium complexes contributes to the formation of the orbital transitions involving iridium atoms, and promotes the enhancement of spin-orbit coupling (SOC) in heavy metals. Based on the efficient exciton transformation channel from the lowest singlet (S1) state to the third triplet (T3) state, the designed 1–3 have smaller energy differences (ΔES1−T3) and larger SOC matrix elements (⟨S1|HSOC|T3⟩) between S1 and T3, resulting in the faster intersystem crossing (ISC) and triplet exciton formation. Furthermore, 1–3/PC71BM heterojunctions with –ΔGCRT