Optimization Of The Photoanode In Efficient CdS Quantum-Dot-Sensitized Photoelectrochemical Photovoltaic Cells

With the increasing global energy demand and the decline of fossil fuel all over the world,as well as the temperature rise caused by global warming,humans are required to work hard continually to develop efficient and cost-effective renewable energy alternatives.Photoelectrochemical photovoltaic cells using semiconductor nanomaterials as photo anodes have attracted much attention.Photoelectrochemical photovoltaic cells convert light energy into electrical energy,which is a feasible way to solve the problems of energy shortage and environmental pollution.Because of the advantages of having both quantum dots and a wide bandgap,CdS-sensitized ZnO has attracted much attention,and has been used in the preparation of photoanode materials for photoelectrochemical photovoltaic cells.However,in the ZnO nanoparticle photoanode,the low stacking property of ZnO prolong the path of electron transport to the conductive substrate,and reduce the number of electrons collected on the conductive substrate.At the same time,the negligible light scattering ability of this photoanode results in relatively poor light capture efficiency.In addition,due to the existence of coordination groups on the surface of CdS quantum dots(QDs)synthesized by organic liquid phase method,the separation and transport efficiency of carriers in quantum dots are reduced,which restricts the further application of this structure in the field of photoelectrochemical photovoltaic cells.In response to the above constraints,focusing on improving the characteristics of ZnO photoanodes in order to improve the photoelectric conversion performance of photoelectrochemical photovoltaic cells,CdS QDs/ZnO nanoparticle photodetectors and CdS QDs/ZnO have been fabricated by preparation process optimization and material structure control.The main research results are as follows:ZnO nanoparticles were prepared as photoanode by hydrothermal method and CdS quantum dots were deposited on the surface by successive ionic layer adsorption and reaction(SILAR),and then it was assembled into a photoelectrochemical ultraviolet detectors(PEC UVPDs).The ZnO nanocrystals before and after CdS QDs sensitization were analyzed by XRD,SEM and EDS.The results show that CdS quantum dots have been attached to the surface of the ZnO nanocrystal film.With the increase of the deposition times and concentration of CdS QDs,the absorbance gradually increases,and the light trapping ability of CdS QDs/ZnO nanoparticle photoanodes is significantly enhanced.Due to the sensitization of CdS QDs,the surface defects of the photoanode film are significantly reduced,and the recombination of carriers also decreases.Based on this,the photocurrent density and switching ratio of the optimized PEC UVPD are 5.311 m A cm^-2 and 2765,respectively.The high crystallinity ZnO nanospheres were prepared by the sol-gel and solvothermal mixing method,and the mesoporous nanostructure has good specific surface area and pore ratio.We used ZnO nanocrystalline particles(NP)with high surface area and ZnO nanospheres(NS)with strong visible light scattering ability to prepare gradient photoanodes and assembled quantum dot sensitized solar cells(QDSSCs).Benefiting from the excellent light scattering performance of ZnO NS in the gradient film,it can increase the light trapping ability of the device.The large specific surface area of ZnO NP can increase the adsorption of CdS QDs and further improve the light trapping ability of the device.The CdS QDs/ZnO NS/NP gradient structure can effectively inhibit the electronic recombination at the ZnO photoanode/electrolyte interface,and further improve the photoelectric conversion performance of the device.Based on this,under the same test conditions,the photoelectric conversion efficiency of the battery reaches 8.2%,which is 17%and 30%higher than the battery efficiency based on pure ZnO NP photoanode and pure ZnO NS photoanode respectively.