Preparation And Photoelectric Properties Of Novel Copper-bismuth-based Multicomponent Sulfide Thin Film Solar Cells

Multi-element thin-film solar cells have good stability because most of the light-absorbing layers are inorganic semiconductor materials.As a branch of multi-component thin-film solar cells,copper-based thin-film solar cells mostly have the advantages of abundant reserves,low cost,simple process,environmental friendliness,strong anti-interference,and high light absorption coefficient,so they have been widely studied.However,the raw materials In and Ga in mainstream copper-based solar cells such as Cu（In,Ga）Se₂（CIGS）are scarce and expensive,while Cu₂Zn Sn（S,Se）₄（CZTSSe）has been extensively studied for many years,and its efficiency is only From 12.6%to 13%.In addition,the use of Cd S buffer layers in both device structures limits the progress of their commercial applications.Therefore,it is imperative to further develop new low-cost thin-film solar cells.Metal Bi is green,non-toxic and chemically stable.By replacing Pb with Bi,perovskite solar cells can not only reduce toxicity but also effectively improve device stability.In this paper,element replacement based on Cu Pb Sb S₃ is used to solve the toxicity problem of the compound.The more environmentally friendly metal Bi is used to replace the congener element Sb,and the Cu Pb Bi S₃ semiconductor thin film is first prepared.Then,by investigating the associated minerals of Cu Pb Bi S₃,it was found that Ag can be used to replace Pb,and the Cu₅Ag Bi₆S₁₂semiconductor thin film was prepared for the first time.The main innovation of this paper is that the photovoltaic performance of two new copper-based semiconductor thin film solar cells,Cu Pb Bi S₃ and Cu₅Ag Bi₆S₁₂,is studied for the first time.The research mainly focuses on the following two aspects:1.Prepare a precursor solution by dissolving Cu,Pb,Bi,and S in thiourea（EDA）and1,2-ethanedithiol（EDT）,and prepare a Cu Pb Bi S₃ thin film by spin coating.The method has the characteristics of low cost,controllable thickness,environment-friendly solution,etc.,and is suitable for large-scale manufacturing of high-efficiency optoelectronic devices.First,the annealing temperature range of the film was obtained by thermogravimetric analyzer（TGA）,and the spin-coating process was optimized to obtain a high-quality film.The secondary phase（Pb S）can then be substantially eliminated by adjusting the Pb/（Cu+Bi）element ratio.On this basis,by further optimizing the ratio of Cu/Bi elements,the secondary phases（Cu S,Bi2S3）can be basically eliminated,and finally a new type of Cu Pb Bi S₃ film with higher purity was synthesized for the first time.The test results of ultraviolet-visible light spectrometer（UV-Vis）show that the optical band gap of Cu Pb Bi S₃ obtained so far is 0.92 e V.Combined with ultraviolet photoelectron spectroscopy（UPS）,the band structure of the film and the semiconductor type are determined.The transient surface photovoltage spectrometer（TSPV）test results show a positive photovoltage signal,which confirms that the obtained new copper-based Cu Pb Bi S₃ thin film sample is an n-type semiconductor,and it is found that the film is rich in Bi and eliminates the secondary phase（Pb S）.Extend the carrier recombination time and increase the carrier concentration.The solar cell was assembled using Cu Pb Bi S₃ thin film,and finally a photoelectric conversion efficiency of 0.17%was obtained.2.Sputtering Cu-Bi alloy and Ag metal element thin film on FTO glass by magnetron sputtering apparatus,and then using a tube furnace to vulcanize the metal thin film with sulfur powder as a sulfur source to prepare Cu₅Ag Bi₆S₁₂ thin film.The film has the characteristics of low cost,green environmental protection and suitable band gap,and is a suitable light absorbing material.High-quality semiconductor thin films were obtained by optimizing the vulcanization process.On this basis,the ratio of（Cu+Bi）/Ag elements was further optimized,the secondary phase was basically eliminated,and a new type of Cu₅Ag Bi₆S₁₂ film with higher purity was obtained for the first time.The optical band gap of Cu₅Ag Bi₆S₁₂ thin film was 1.23 e V obtained by UV-Vis test,and the energy band structure and carrier lifetime of the thin film were determined by combining UPS and TSPV,and it was found and verified that the material was a p-type semiconductor.On this basis,the device was assembled and the performances of Spiro-OMe TAD and P3HT as hole transport layerswere compared.Finally,with the FTO/Ti O₂/Cu₅Ag Bi₆S₁₂/P3HT/Au device structure,a PCE of 0.07%was initially obtained.