Enhanced charge trapping effect in PVA/PbI2 synaptic transistors achieved through integrated UV irradiation and thermal annealing treatments

Abstract

Charge-trapping synaptic transistors, owing to their excellent non-volatility, controllable channel conductance, and switching performance, have garnered widespread attention as promising candidates for neuromorphic devices. In this study, the underlying PVA film can smooth the surface of the PbI₂ film, thus decreasing its surface roughness and alleviating the charge trapping phenomenon at the PbI₂/IGZO heterojunction. The PVA/PbI₂ charge-trapping synaptic transistors exhibit progressively enhanced charge-trapping capacity with increasing PbI₂ thickness, attributed to the elevated concentration of iodine vacancies (V_I) within the PbI₂ layer. Moreover, the synergistic combination of UV irradiation and thermal annealing can significantly enhance the charge trapping capability of PVA/PbI₂ synaptic transistors because it induces the decomposition of PbI₂ and the formation of PbO, thus modulating the concentration of V_I. At a lower UV irradiation intensity of 87.5 mW cm⁻², the hysteresis window of the devices initially increases, then decreases with increasing temperature. In contrast, when the UV irradiation intensity is elevated to 122.5 mW cm⁻², the hysteresis window shows a monotonic decrease with increasing temperature. When the UV irradiation intensity was maintained at 87.5 mW cm⁻² and the thermal annealing temperature at 150 °C, the device demonstrated a substantial hysteresis window of 8.56 ± 0.34 V (V_G: −10–10 V). Finally, the PVA/PbI₂ charge-trapping synaptic transistor manifested typical synaptic characteristics. The image recognition accuracy reached as high as 90.1% after 40 training epochs. This suggests that PVA/PbI₂ synaptic transistors hold considerable promise in the fields of neuromorphic computing and artificial intelligence (AI).