The Preparation Of Er-doped Carbon Quantum Dots And The Applied Reseach In CdS Quantum Dots Sensitized Solar Cells

The solar energy utilization is a promising method to solve the problem of energy crisis.In the current methods of solar energy utilization,solar cell is one of the most feasible technologies,which can convert the solar energy to electrical energy.Quantum dot sensitized solar cells?QDSSCs?have been considered as next generation of solar cell.Developing high performance of QDSSCs is one of the most promising methods to meet the imperative societal need for sustainable clean energy with minimal or no detrimental environment hazards.At present,many quantum dot materials have been used in QDSSCs,for example,CdS,CdSe,PbS.Among them,CdS quantum dot has the narrow band gap and superior stability,which makes it become an attractive sensitizer in QDSSCs.However,so far the power conversion efficiency of CdS QDSSCs still much lower than that people expected.At present stage,many problems still restrict the enhancement of photovoltaic performance of CdS QDSSCs.Firstly,the light absorption capacity of CdS is small and the light absorption range is narrow.Secondly,the charge separation is incomplete and electron collection efficiency is low.Therefore,in order to improve the energy conversion efficiency of CdS QDSSCs,It is necessary to widen the range of light response of CdS QDSSCs and improve the efficiency of charge separation.As a new class of carbon material,carbon quantum dots?CQDs?are widely used in many fields because of their good optical properties and excellent conductivity.Firsly,CQDs can emit blue light under the ultraviolet light irradiation.Besides,a large number of conjugated?bonds exist in the structure of CQDs,which makes is posseess good electron transport properties.Thus,we consider introducing CQDs into CdS QDSSCs in our experimental group.In this study,Er-CQDs were prepared by the reflux and hydrothermal methods.CdS/TiO₂,CdS/CQDs/TiO₂ and CdS/Er-CQDs/TiO₂ photoanodes were prepared by sol-gel,spin-coating and successive ionic layer adsorption and reaction?SILAR?methods,respectively.The structure and optical properties of Er-CQDs were investigated in detail by FT-IR UV-vis and FL.The structure,morphology,composition and optical property of the photoanodes of CdS QDSSCs were investigated by XRD,EDX,SEM,TEM,UV-vis and PL technologies.The photovoltaic properties of CdS QDSSCs based on different photoanodes?CdS/TiO₂,CdS/CQDs/TiO₂ and CdS/Er-CQDs/TiO₂?have been studied by electrochemical method.Besides,the working principle of CdS QDSSCs based on CdS/Er-CQDs/TiO₂ photoanode was proposed.It can be found that Er-CQDs have a stronger light absorption capacity than that of CQDs in the UV to blue light region.Introduction of Er³⁺can broden the light absorption range of CQD,especially in the visible region.Under the excitation of the same wavelength,the emission peak intensity of Er-CQDs is much higher than that of CQDs.The emission peaks of Er-CQDs are concentrated at 450 nm in the range of excitation wavelength from 350 nm to 550 nm.By introducing Er-CQDs into CdS QDSSCs,we can find that the photo-response range of the photoanode is widened,and the charge recombination efficiency of CdS quantum dots is decreased.At the same time,the introduction of Er-CQDs can accelerate the electron transfer from CdS quantum dots to TiO₂,which greatly improves the photovoltaic performance of CdS QDSSCs.