From Organic Afterglow to Phototransistor Memory via Trap‐Controlled Charge Kinetics

ABSTRACT

Organic afterglow exploits photo‐induced electron transfer (PIET) and diffusion‐/transport‐limited charge recombination to produce long‐lasting emission. Because the kinetics are governed by charge separation, trapping/detrapping, and delayed recombination, they can be tuned by donor–acceptor redox strength, composition, and radical stability, thereby offering an optical approach to studying trap‐regulated charge dynamics. In parallel, organic phototransistor memory (OPTM) aims to enhance photoinduced charge separation and to stabilize trapped carriers at the channel/electret interface, thereby achieving high photosensitivity and long retention. Guided by this shared trap‐controlled framework, we develop an afterglow‐emissive electret based on a triphenyl‐triazine‐functionalized polymer donor (PPTZ) with a deep HOMO level, interacting with cationic photocatalyst acceptors in OPTM. Photoexcitation triggers PIET from PPTZ to the acceptors, forming trapped holes in the PPTZ matrix and long‐lived radical species that recombine slowly, thereby yielding persistent emission and promoting the device's photoresponse. Notably, the optimal OPTM achieves a photosensitivity of 1.2 × 10 ⁷ and a high memory ratio > 10 ⁴ . Regarding weak‐light detection, the optimal OPTM achieves a maximum responsivity of 2786 A W ⁻¹ and specific detectivity of 4.1 × 10 ¹⁴ Jones. Overall, this work establishes a universal, unified design strategy that links trap‐mediated afterglow emission to trap‐modulated OPTM operation for high‐performance memory.