Preparation And Photoelectric Properties Of CdSe Nanocomposites

Quantum dot sensitized solar cells have become a hotspot in scientific research today due to their simple preparation process,low cost,and high theoretical conversion efficiency.At present,the wide band-gap semiconductor oxides commonly used in quantum dot sensitized solar cell structures are mainly TiO₂,ZnO and SnO₂.However,they can only absorb light in the ultraviolet region due to their large band-gap,thus affecting the photoelectric conversion efficiency of the cell.In order to solve this problem,the common method is to use a narrow band gap semiconductor as a sensitizer to sensitize an oxide.In this paper,a narrow bandgap semiconductor CdSe（1.7 eV）is used instead of a wide band gap semiconductor oxide as the substrate of quantum dot sensitized solar cells,and PbS（0.4 eV）and Ag₂S（1.1 eV）quantum dots are used as sensitizers to sensitize them.Finally,the widening of the light absorption range and the improvement of the photoelectric conversion performance of the CdSe photoelectrode are realized.This paper has carried out the following three aspects of work.1.The CdSe nanorod array film was prepared by electrodeposition method.After annealing at a certain temperature,the CdSe nanorod array was sensitized with successive ion layer adsorption（SILAR）method using PbNO₃ and Na₂S as Pb⁺and S^2-ion sources,respectively.CdSe/PbS nanocomposites were prepared.The sample was then characterized by a series of characterizations and its photoelectric conversion properties were explored.The experimental results show that when the number of PbS quantum dot sensitization cycles reaches 6（CdSe/PbS（6C））,the photocurrent density is the largest,the value is 6.25 mA/cm²,and the photoelectric conversion efficiency is 1.2%.2.In order to reduce the recombination of photogenerated electron-hole pairs and further improve the photoelectric performance of the CdSe/PbS photoelectrode,a method of adding a ZnS passivation layer to the CdSe/PbS photoelectrode is adopted.CdSe/PbS/ZnS nanocomposites were prepared by SILAR method using Zn（CH₃COO）₂ and Na₂S as Zn²⁺and S^2-ion sources,respectively.The sample was then characterized by a series of characterizations and its photoelectric conversion properties were explored.The experimental results show that compared with pure CdSe and CdSe/PbS,the photocurrent density of CdSe/PbS/ZnS nanocomposites is significantly improved,the value is 9.44 mA/cm²,and the photoelectric conversion efficiency is 2.8%.3.CdSe/Ag₂S nanocomposites were prepared by sensitizing CdSe nanorod arrays with SILAR method with AgNO₃ and Na₂S as ion sources of Ag⁺and S^2-.The sample was then characterized by a series of characterizations and its photoelectric conversion properties were explored.The experimental results show that when the number of Ag2S quantum dot sensitization cycles reaches 5（CdSe/Ag2S（5C））,the photocurrent density is the largest,the value is 36.88 mA/cm²,and the photoelectric conversion efficiency is 6.8%.