Dual-Mode Photonic Synapse Based on a Lead-Free 2D Ruddlesden–Popper Perovskite for Neuromorphic Vision

Inspired by the human visual system, photonic synapses with photonic sensing and data memorization offer a promising alternative to traditional von Neumann architectures for neuromorphic computing. This study introduces a multifunctional artificial photonic synapse based on solution-processed PEA₂SnI₄ 2D Ruddlesden-Popper perovskite. By modulation of the applied bias voltage, the PEA₂SnI₄ device can switch between two distinct optoelectronic modes. In the absence of bias, the device operates in the photodetector mode, demonstrating a responsivity of 42.4 mA W^-1. The low dark current of the device allows for a high detectivity of 3.6 × 10¹⁴ Jones and a broad linear dynamic range of 140 dB. Under reverse bias, the device transitions into a synaptic mode, enabling the observation of several synaptic behaviors, including paired-pulse facilitation, long-term potentiation, spike-frequency-dependent plasticity, and spike-number-dependent plasticity. The synaptic behavior is attributed to band alignment and carrier accumulation in the interfacial layer. Moreover, the synaptic performance of the PEA₂SnI₄ device is further illustrated through simulations of image contrast enhancement and edge detection. This work reveals the potential of PEA₂SnI₄-based photonic synapses for next-generation neuromorphic vision systems, offering an energy-efficient and highly adaptable approach to optoelectronic computing applications.