Photoelectric devices are extensively applied in optical logic systems, light communication, optical imaging, and so on. However, traditional photoelectric devices can only generate unidirectional photocurrent, which hinders the simplification and multifunctionality of devices. Recently, it has become a new research focus to achieve controllable reversal of the output photocurrent direction (bipolar current) in a photoelectric system. Considering that the device with bipolar current adds a reverse current operating state compared to traditional devices, the former is more suitable for developing new multifunctional photoelectric devices. Due to the existence of electrolytes, photoelectrochemical (PEC) systems contain chemical processes such as ion diffusion and migration and electrochemical reactions, which are unable to occur in solid-state transistor devices, and the effect of electrolyte pH on the performance of PEC systems is usually ignored. We prepared a MnPS3-based PEC-type photodetector and reversed photocurrents by adjusting the pH of electrolytes, i.e., the electrolyte-controlled photoelectrochemical photocurrent switching (PEPS) effect. We clarified the effect of pH values on the direction of photocurrent from the perspectives of electrolyte energy level rearrangement splitting and the kinetic theory of the semiconductor electrode. This work not only contributes to a deeper understanding of carrier transport in PEC processes but also inspires the development of advanced multifunctional photoelectric devices.
Here, we systematically report on the preparation of high-quality few-layered MnPS3 nanosheets (NSs) by chemical vapor transport (CVT) and mechanical stripping method, and its carrier dynamics and third-order nonlinear optical properties were studied. Using the classical technique of open aperture Z-scan, a typical phenomenon of saturable absorption (SA) was observed at 475 nm, which indicates that the material is expected to be used as a saturable absorber in ultrafast lasers. The typical phenomenon of reverse saturation absorption (RSA) is observed at 800 and 1550 nm, which shows its potential in the field of broadband optical limiting. Compared with graphene, BP, MXene, MoS2 and other typical two-dimensional materials, MnPS3 NSs has a higher modulation depth. Using the non-degenerate transient absorption spectroscopy technology at room temperature, a slower cooling process of thermal carrier of MnPS3 was observed. Moreover, the carrier lifetime can be tuned according to the wavelength. This work is of great significance to the improvement of MnPS3 based devices, and lays a foundation for the application of MnPS3 in short-wavelength photovoltaic cell, photoelectric detection and other fields.
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