Photoelectrochemical Functional Devices Based On Bi Nanosheets/BP Quantum Dot Heterojunction And Its Performances

Bismuth(Bi)materials have a broad application prospect in the field of optoelectronic because of its narrow tunable bandgap(0.99 e V for monolayer Bi and0.03～0.04 e V for counterpart bulk material)and high carrier mobility.However,it is very important to enhance the optical absorption ability of bismuth material for its practical application.Instead,zero-dimensional(0D)quantum dots(QDs)are considered to as low-cost and effective materials for improving light absorption capacity because of its inherent surface effect and quantum confinement effect.Recently,black phosphorus(BP)QDs which has the advantages of non-toxicity,environmentally friendly and moderate strong optical absorption,have been widely used in optoelectronic devices.In this paper,Bi nanosheets(NSs)and BP QDs were used as the main materials,and the required materials were obtained from chunk by simple liquid exfoliation method.Subsequently,Bi NSs/BP QDs heterojunctions were constructed via a facile sonication approach.A series of characterization methods,including Scanning Electron Microscope(SEM),Transmission Electron Microscope(TEM)and Raman spectrum et al.,were adopted to observe the microstructure and analyze the composition of as-prepared Bi NSs,BP QDs and Bi NSs/BP QDs mixed materials.Based on as-prepared Bi NSs/BP QDs heterojunctions hybrid materials,we explored its applications in photodetectors and pH sensors.The main contents are as follows:1.A simple and effective sensor prototype was prepared by using Indium Tin Oxides(ITO)film as conductive substrate and Bi NSs/BP QDs heterojunction as photosensitive material,respectively.The functional relationship between the photocurrent density and pH value of as-fabricated device was established by electrochemical test with sodium hydroxide(Na OH)solution as pH reagent.The measurement results show that compared with Bi NSs-based sensor,Bi NSs/BP QDs heterojunctions-based sensor has a greater linear correlation coefficient between the photocurrent density and pH value,and has good stability in alkaline solution.These experimental results show that the Bi NSs/BP QDs heterojunction-based pH sensor has excellent alkaline pH sensing characteristics,which provides basic research for the application of Bi NSs/BP QDs heterojunction in pH sensing.2.The flexible photoelectrochemical(PEC)-type photodetector was constructed by using solid electrolyte as conductive medium,conductive Polyethylene Terephthalate(PET)film as conductive substrate and Bi NSs/BP QDs heterojunction as photosensitive material,respectively.The as-fabricated Bi NSs/BP QDs-based photodetectors exhibit 4.6μA/cm~2 photocurrent density at applied 0.8 V bias potential,about 4.2 times enhancement compared to Bi NSs.Additionally,the photocurrent density of Bi NSs/BP QDs-based photodetectors reaches to 100 n A/cm~2 without external power supply,allowing fabricated devices to work normally in an emergency.Meanwhile,long-cycle stability measurements reveal 15%photocurrent density attenuation after 2000 bending times and 8.8%under 60°bending angles.These results show that the introduction of BP QDs significantly improves the photoresponse performance of Bi NSs-based photodetectors,demonstrating the great application prospect of BP QDs in the field of photodetectors and providing a new strategy for the construction of flexible photodetectors.