The Polymer Society of Korea

Abstract

We report air-stable organic photodetectors (OPDs) based on immiscible planar heterojunction (PHJ) interfaces that address the nanomorphology instability of conventional bulk heterojunction (BHJ) and pseudo-PHJ OPDs. A random polythiophene donor (RP-T50) with ≈50 mol% thermocleavable side chains (TCSs) and PC₇₁BM acceptor were employed. Thermal annealing cleaved the TCSs, forming insoluble RP-T50-COOH films and stable, unmixed PHJ interfaces with PC₇₁BM, thereby suppressing pseudo-PHJ formation. The insoluble donor layer enabled fully green-solvent processing and achieved a responsivity of ≈138 mA W^-1, a detectivity of ≈1.68 × 10¹² Jones, and a linear dynamic range of ≈100 dB at zero bias. Notably, the devices retained performance for ≈250 days under ambient conditions without encapsulation. This work demonstrates a simple and scalable strategy to enhance OPD air stability toward practical commercialization.