Impact of Thermal Stress on Device Physics and Morphology in Organic Photodetectors
Hoang Mai Luong, Sangmin Chae, Ahra Yi, Kan Ding, Jianfei Huang, Brian Minki Kim, Claire Welton, Jingcong Chen, Hiba Wakidi, Zhifang Du, Hyo Jung Kim, Harald Ade, G. N. Manjunatha Reddy, Thuc‐Quyen Nguyen
Abstract
Organic photodetectors (OPDs) capable of detecting visible to near-infrared light provide a ubiquitous platform for emerging flexible and wearable electronics. In the process of implementing OPDs into a Si-based manufacturing process, organic semiconductors undergo ≥ 200 °C thermal stress, leading to the deterioration of photosensing capability. Here, we combine multiscale characterization and device physics to unravel the impact of thermal stress on the optoelectronics characteristics of PTB7-Th:non-fullerene acceptor blends (NFAs: SiOTIC-4F, COTIC-4F, CO1-4F, and CO1-4Cl). For as-cast devices, favorable intermixing and phase separation between PTB7-Th and the NFA facilitate charge generation and extraction. Reductions in the OPD performance after thermal annealing (200 °C for 5–120 min) are observed due to the morphological degradation, regardless of the NFA choice, but the reduction is more severe for the PTB7-Th:SiOTIC-4F blend. Thermally induced morphological changes are examined using atomic force microscopy, wide-angle X-ray scattering, and solid-state NMR spectroscopy. This study provides essential insights into morphology-driven deteriorations, which will help in developing structure–stability–performance relationships in high detectivity OPDs.