Strong Polarons Enable High-Performance Perovskite Optoelectronic Synaptic Diode Array for In-Sensor Computing

Halide perovskites, with their outstanding photovoltaic properties, are ideal materials for constructing optoelectronic synaptic diodes (OSDs) in in-sensor computing. High recognition accuracy requires OSDs to generate a large number of photoresponsivity states and have a high light-to-dark current ratio (I_light/I_dark) for reliable signal discrimination. However, current perovskite OSDs that rely on ion migration and band-offset barrier to localize carriers are limited by the number of photoresponsivity states (< 300) and I_light/I_dark (< 10³). Here, we propose a novel mechanism that utilizes strong polarons in halide perovskites to simultaneously overcome these two limitations. We incorporate a strong polar organic amine, 3,5-diaminobenzoic acid (mDAC), into MAPbI₃ to form an mDACPbI₄/MAPbI₃ heterostructure as the active layer of OSDs. The large dipole moment of mDAC enhances the strength of polarons in the heterostructure, which can localize more carriers, thereby achieving 1329 accessible photoresponsivity states and 723 distinguishable photoresponsivity states. Moreover, mDAC suppresses ion migration, improving photovoltaic performance, which enables a high I_light/I_dark of 10⁴ at 0 V. Both the I_light/I_dark and the number of photoresponsivity states are among the best reported performance of OSDs. Furthermore, we construct an 11 × 11 flexible crossbar array to demonstrate real time digit recognition, highlighting its potential for in-sensor vision systems.