Band Gap Oxide Photoanode Modification And Its UV Detection Performance

Owing to the arising demand for precise detection of ultraviolet radiation in civil and military applications,the development of ultraviolet photodetectors with energy efficiency,a sustainable optical energy detection system,and essential and cost-effective wide bandgap material have become vital.Si-based photodetectors,relying on p-n type semiconductor homojunction technology,are commonly established in commercial market for detection of ultraviolet light.These UV detectors have some significant limitations including the requirement of long-pass filters to block low energy photons and cooling systems to reduce noise and leakage current,high operation voltage.This significantly hampers their integration in Si technologies and alternative approaches are thoroughly sought after.Hence,the self-powered UV photodetectors based on photoelectrochemical cells（PEC）that function as self-powered,wirelessly,independently and sustainably,have emerged as important type of optoelectronic devices to convert photon within a range of wavelengths into detectable current based on their material properties.These distinctive characteristics make PEC-type self-powered UVPDs as attractive candidates for practical applications to alleviate the energy crisis challenges for humanity.Besides the above characteristics,the self-powered PEC-UVPDs exhibits low cost,simple fabrication process and fast response.Herein,we explored the fabrication of photoelectrochemical-type self-powered UV photodetectors based on wide band-gap materials namely:SnO₂,TiO₂ and ZnO.This study is aimed at improving the performance of PEC-type self-powered UVPD by minimizing the electron charged recombination at the interface between metal oxide/redox electrolyte.These wide band gap materials have been considered owing to their remarkable optical and electrical properties for possible applications in optoelectronics and photonics.However,the electrons transferred between these metal oxides layer and their oxidized redox couples electrolyte such as I₃^-,have high tendency to recombine.To overcome this limitation,plasmonic Ag/rGO hybrid composite,Ag@SnO₂ nanoparticles and TiCl₄-surface treatment were introduced as effective surface modification approach to modify these metal oxide photoanodes films.The details are as follows:Silver–reduced graphene oxide（Ag/rGO）was synthesized by modified hydrothermal method and incorporated into SnO₂ nanorods as photoanode materials for self-powered PEC-UVPDs.The effect of plasmonic Ag/rGO hybrid composite on SnO₂ photoanodes for the performance of PEC-UVPDs were investigated in detail.The optimized 1.0 wt.%Ag/rGO incorporated into SnO₂-based UVPD shows a significant photocurrent response due to the enhanced absorption light and effective suppression of charge recombination.This UVPD demonstrates a high performance,with photocurrent density reaching 0.29m A·cm^-2 compared to the SnO₂-based device with 0.16 mA·cm^-2.This device also exhibits a high on:off ratio of 195 and fast response time,which are superior to that of the free-modified one,making this device favorable in ultraviolet detection.Ag@SnO₂ NPs have been prepared by varying the concentration of sodium stannate trihydrate coated onto ZnO nanorods as photoanode for a photoelectrochemical self-powered ultraviolet photodetector.The effect of plasmonic Ag@SnO₂ NPs on ZnO photoanodes for the performance of PEC-UVPDs were investigated in detail.This PEC self-powered UVPD exhibits enhanced ultraviolet photoluminescence to nearly 6 orders when 2 mL of 40 mM sodium stannate trihydrate is used.This enhancement in photoluminescence intensity is attributed to the localized surface plasmon resonance of Ag in Ag@SnO₂.Furthermore,when varying sodium stannate trihydrate concentration in Ag@SnO₂ NPs,the UVPD with 2 mL of 40 mM sodium stannate trihydrate displays a high photocurrent density(J_sc)of 5.81 mA·cm^-2 compared to ZnO UVPD with 2.34 mA·cm^-2.This boosting in photocurrent is ascribed to the enhanced UV light harvesting and suppression in interfacial charge recombination.Moreover,this device also shows a high on/off ratio of 3885 and fast response time which are higher than ZnO UVPD.Finally,the Ag@SnO₂ nanoparticles coated on ZnO NRs can be used as a promising photoanode for high-sensitive PEC-type self-powered UVPDs.TiCl₄ surface-treated SnO₂ photoanodes were employed to fabricate PEC self-powered UV photodetectors.The influence of TiCl₄-surface treatment on SnO₂ photoanodes for the performance of PEC-UVPDs were investigated in detail.It is found that the TiCl₄-treated SnO₂-based UVPD shows a higher photocurrent density（J）and open-circuit voltage compared to the pure SnO₂-based UVPD.The TiCl₄-treated SnO₂-based UVPD has a high on/of ratio of 6475,rapid response（0.009 s for rise time and 0.006 s for decay time）,excellent spectral selectivity and linear optical signal response under UV light irradiance.In addition,TiCl₄ pre-&post-treated TiO₂ nanocrystal films were applied as photoanodes for PEC self-powered.The TiCl₄ pre-&post-treated TiO₂-based UVPD with PEC also exhibits a high photocurrent density and open-circuit voltage compared to that of UVPD-based on un-treated TiO₂ films.Under UV light irradiance,the TiCl₄ pre-&post-treated TiO₂ based UVPD demonstrate superior performance with a high on/off ratio of 11718,fast response time（rise time of 0.009 s and decay time of 0.017 s for J signal）and excellent linear optical signal response.These results indicate that the plasmonic Ag/rGO hybrid composite,Ag@SnO₂ core-shell nanoparticles and TiCl₄ surface treatment are effective strategy to improve the performance of photoelectrochemical UVPDs.