Suppression of Tin Oxidation via Sn→B Bonding Interactions for High-Resolution Lead-Free Perovskite Neuromorphic Imaging Sensors.

Abstract

Lead-free tin-based perovskites, specifically (4-Cl-PEA)₂SnI₄, possess significant potential for the development of high-performance, robust neuromorphic imaging sensors, owing to their superior optoelectronic properties and compatibility with conventional complementary metal-oxide-semiconductor fabrication techniques and silicon-based readout circuits. However, the excessive oxidation of Sn²⁺ remains a significant obstacle, leading to suboptimal synaptic performance and low resolution in the neuromorphic imaging sensors due to increased recombination losses and poor film uniformity. This study first demonstrates that the introduction of novel Sn→B donor-acceptor bonding interactions effectively suppresses Sn²⁺ oxidation, enhancing uniformity, reducing nonradiative recombination, and improving synaptic plasticity. A vertical optoelectronic synapse demonstrates diverse synaptic behaviors, attributed to hole trapping and detrapping at the device interface. Additionally, the device enables applications in associative learning, neuromorphic computation, letter encoding, and handwritten digit recognition. Ultimately, integration with silicon circuits results in a high-resolution (32 × 32) neuromorphic imaging array, one of the highest reported resolutions for perovskite optoelectronic synapse arrays. The improved uniformity of boric acid-added (4-Cl-PEA)₂SnI₄ perovskite films significantly reduces photo response non-uniformity, enhances resolution, and improves memory capabilities. This neuromorphic imaging array successfully integrates sensing, storage, and computation, enabling advanced functionalities like letter recognition, memory, and processing, surpassing conventional image sensors.