A lead-free two-dimensional perovskite for a high-performance flexible photoconductor and a light-stimulated synaptic device

Organo-lead halide perovskites have emerged as promising materials for high-performance photodetectors. However, the toxicity of lead cations in these materials limits their further applications. Here, a flexible photoconductor is developed based on lead-free two-dimensional (2D) perovskite (PEA)₂SnI₄via a one-step solution processing method. The flexible transparent electrodes are patterned from rGO/(PEDOT:PSS) hybrid films. The stability and reproducibility of the devices are significantly improved on adding 30 mol% SnF₂ to the perovskite. The flexible photoconductors show a photoresponsivity of 16 A W^-1 and a detectivity of 1.92 × 10¹¹ Jones under 470 nm illumination, which are higher than those of most of the similar devices. Besides, the devices possess much better mechanical flexibility and durability than the flexible devices with an Au electrode. Finally, this flexible photoconductor is applied as a light-stimulated synaptic device and can mimic the short-term plasticity of biological synapses. This is the first study to report that lead-free 2D perovskite can be used in flexible photoconductors and synaptic devices.