The development of negative photoconductivity (NPC)-related devices is of great significance for numerous applications, such as optoelectronic detection, neuromorphic computing, and optoelectronic synapses. Here, an unusual but interesting NPC phenomenon in the novel cesium cobalt chlorine (Cs₂CoCl₄) single crystal-based optoelectronic devices is reported, which simultaneously possess volatile resistive switching (RS) memory behavior. Joint experiment−theory characterizations reveal that the NPC behavior is derived from the intrinsic vacancy defects of Cs₂CoCl₄, which could trap photogenerated charge carriers and produce an internal electric field opposite to the applied electric field. Such NPC effect enables an abnormal photodetection performance with a decrease in electrical conductivity to illumination. Also, a large specific detectivity of 2.7 × 10¹² Jones and broadband NPC detection wavelength from 265 to 780 nm were achieved. In addition to the NPC response, the resulting devices demonstrate a volatile RS performance with a record-low electric field of 5 × 10⁴V m⁻¹. By integrating the characteristics of electric-pulse enhancement from RS and light-pulse depression from NPC, an artificial optoelectronic synapse was successfully demonstrated, and based on the simulation of artificial neural network algorithm, the recognition application of handwritten digital images was realized. These pioneer findings are anticipated to contribute significantly to the practical advancement of metal halides in the fields of in-memory technologies and artificial intelligence.

负光电导 （NPC） 相关器件的开发对于众多应用具有重要意义，例如光电检测、神经形态计算和光电突触。在这里，报道了新型铯钴氯 （Cs₂CoCl₄） 单晶基光电器件中一种不寻常但有趣的 NPC 现象，它们同时具有易失性电阻开关 （RS） 记忆行为。联合实验理论表征表明，NPC 行为源自 Cs₂CoCl₄ 的本征空位缺陷，它可以捕获光生载流子并产生与施加电场相反的内部电场。这种 NPC 效应会导致光检测性能异常，同时降低对照明的电导率。此外，还实现了 2.7 × 10¹² Jones 的大特异性检测率和 265 至 780 nm 的宽带 NPC 检测波长。除了 NPC 响应外，所得器件还表现出不稳定的 RS 性能，具有创纪录的 5 ×^{10 4} V ^m-1 的低电场。通过整合 RS 的电脉冲增强和 NPC 的光脉冲抑制特性，成功演示了人工光电突触，并基于人工神经网络算法的仿真，实现了手写数字图像的识别应用。预计这些开创性的发现将为金属卤化物在内存技术和人工智能领域的实际进步做出重大贡献。