Two-dimensional Bismuthene Based Photoelectrochemical-type Flexible Photodetector And Its Performances

As a new type of self-powered photodetector,the photoelectrochemical type(PEC)photodetector can work without external power,owing to the influence of the special dynamic mechanism formed by the contact between electrons and holes due to solidliquid contact,directional electron movement will occur to generate current.In addition,because of its low production cost and the progress of simple manufacturing process,it is more promising in various self-powered photodetectors.However,ordinary PEC photodetectors work in a liquid electrolyte environment with a three-electrode system.This complex system increases the weight and volume of the photodetector,which will limit the practical application in flexible electronic devices.Therefore,if the PEC photodetector can be manufactured as a portable solid device with flexible characteristics,it will be of great significance to develop a new type of photoelectric device.As a key component of flexible devices,photosensitive materials are important factors that affect the performance of flexible devices.However,traditional rigid materials are fragile and easily damaged after repeated folding,resulting in poor performance of flexible devices and other factors that limit the practical application of flexible devices.In recent years,two-dimensional materials have been popular in the field of materials science.Due to the atomic thickness,the carrier migration and heat diffusion on the surface are restricted to the two-dimensional plane,thus exhibiting many peculiar physical and chemical properties.In addition,compared with bulk materials,two-dimensional materials have good flexibility and ductility,which makes them have good development prospects in the field of flexible devices.Bismuthene,with a lattice structure similar to graphene,is an emerging semi-metallic or semiconductor material with adjustable band gap(0.32-0.8 e V)and extremely high carrier mobility.Moreover,it has preferable stability in the air environment which is considered to have good application prospects in the field of optoelectronic devices.In this paper,high-quality bismuth nanosheets are mainly obtained by liquid-exfoliation which are used as photosensitive materials,and photoelectrochemical photodetectors are used as research objects.By using solid electrolytes to replace traditional electrolytes,portable photoelectrochemical photodetectors are realized.To this end,we used the two-dimensional liquid peeled bismuth nanosheets as flexible and sensitive materials for the device.In addition,we propose a method to replace the traditional electrolyte with a quasi-solid electrolyte,and construct a flexible all-solid electrochemical photodetector with a sandwich structure.Compared with the traditional PEC photodetector with liquid electrolyte,it greatly reduces the volume of the electrochemical photodetector.In addition,the quasi-solid electrolyte can be better shaped and adapted to different surfaces,and can prevent electrolyte leakage during device folding,which is an important factor for flexible devices.By using flexible indium tin oxide(ITO)as the substrate and two-dimensional bismuth nanosheets as the photosensitive material,the photodetector made has excellent flexibility,bendability and expandable durability.Bending stability tests have shown that under different bending angles and after 120 bending cycles,there is no significant attenuation compared with the original photocurrent density,which shows considerable advantages in wearable and flexible electronic applications.