Neuromorphic computing simulates the operation of biological brain function for information processing and can potentially solve the bottleneck of the von Neumann architecture. This computing is realized based on memristive hardware neural networks in which synaptic devices that mimic biological synapses of the brain are the primary units. Mimicking synaptic functions with these devices is critical in neuromorphic systems. In the last decade, electrical and optical signals have been incorporated into the synaptic devices and promoted the simulation of various synaptic functions. In this review, these devices are discussed by categorizing them into electrically stimulated, optically stimulated, and photoelectric synergetic synaptic devices based on stimulation of electrical and optical signals. The working mechanisms of the devices are analyzed in detail. This is followed by a discussion of the progress in mimicking synaptic functions. In addition, existing application scenarios of various synaptic devices are outlined. Furthermore, the performances and future development of the synaptic devices that could be significant for building efficient neuromorphic systems are prospected.

Zinc Oxide (ZnO) has been regarded as a promising electron transport layer (ETL) in perovskite solar cells (PSCs) owing to its high electron mobility. However, the acid-nonresistance of ZnO could destroy organic-inorganic hybrid halide perovskite such as methylammonium lead triiodide (MAPbI3) in PSCs, resulting in poor power conversion efficiency (PCE). It is demonstrated in this work that Nb2O5/ZnO films were deposited at room temperature with RF magnetron sputtering and were successfully used as double electron transport layers (DETL) in PSCs due to the energy band matching between Nb2O5 and MAPbI3 as well as ZnO. In addition, the insertion of Nb2O5 between ZnO and MAPbI3 facilitated the stability of the perovskite film. A systematic investigation of the ZnO deposition time on the PCE has been carried out. A deposition time of five minutes achieved a ZnO layer in the PSCs with the highest power conversion efficiency of up to 13.8%. This excellent photovoltaic property was caused by the excellent light absorption property of the high-quality perovskite film and a fast electron extraction at the perovskite/DETL interface.

Through combining a four-point probe and an optical technique, a profound vanadium(v) size effect on the change in excess resistivity during hydrogenation is observed in Fen/V7n (n = 2, 4) superlattices at c ≥ 0.05 H/V.