High Conduction Band Polymer Acceptor as a Ternary Component for Indoor Power Generation and Photodiode: Enhanced Photovoltage and Suppressed Dark Current

We explore the application of a high conduction band polymer acceptor (IDSIC-BTI) as a ternary component in indoor organic photovoltaic cells (IOPVs) and organic photodiodes (OPDs). IDSIC-BTI shows a 1.91 eV electrochemical band gap and a high-lying lowest unoccupied molecular orbital (LUMO) of −3.78 eV. Its compatibility and miscibility with nonfullerene acceptors (NFAs) stem from shared electron-deficient structural elements. Combining IDSIC-BTI with NFAs such as IT-4F and Y6 yields smooth surface morphologies and elevates LUMO levels due to the formation of acceptor–acceptor (A–A) alloys. This heightened LUMO level within the A–A alloy structure contributes to the expansion of the energy gap associated with charge-transfer states (ECT) in ternary blends using PM6 as a donor polymer. As a direct consequence of this effect, these ternary blends exhibit an increased open-circuit voltage (VOC) and decreased dark current density (JD). For IOPV applications, incorporating IDSIC-BTI into the PM6:IT-4F blend enhances the VOC (from 0.70 to 0.75 V) and raises power conversion efficiency from 20.9 to 22.9%. In OPD devices, the ternary PM6:Y6:IDSIC-BTI blend demonstrates a 1.7 times higher specific detectivity of 5.71 × 1012 Jones compared to binary OPD while effectively reducing JD. These findings may suggest effective strategies for regulating VOC and JD in IOPV and OPD devices through the strategic inclusion of a third component.