Preparation Of Electron Transport Layer Of Perovskite Solar Cells By Vacuum Ultraviolet Technolog

Perovskite solar cells（PSCs）with the advantages of low-cost,facile solution process and excellent photovoltaic property have attracted extensive attentions,and become the promising candidate for next generation photovoltaic device.The power conversion efficiency（PCE）of PSCs has been unprecedentedly boosted to the newly recorded 25.8%,however,there is still a lot of room to attain the theoretical efficiency limit of Shockley-Queisser.The ETL plays an important role in PSCs,it can not only connect the perovskite layer and the transparent electrode to speed up the electron transport,but also inhibit the recombination of charge carriers.TiO₂is widely utilized as ETL of PSCs due to the characteristics of low cost,nontoxicity and suitable band energy level with halide perovskite materials.However,a high temperature sintering process is required to improve the electron mobility of TiO₂.In order to further improve PCE of PSCs,In this thesis,the compact TiO₂thin films for the PSCs ETL were fabricated by 172 nm vacuum ultraviolet（VUV）light technology,which significantly improved the mobility of photogenerated electrons,effectively inhibited the recombination of photogenerated charges,and then improved the photoelectric performance of PSCs.The main research contents are as follows:（1）Titanium oxygen-containing metal organic films were prepared with titanium diisopropyl diacetylacetone as precursor,and TiO₂films were prepared by irradiation of the precursor thin films with VUV light in a short time at low temperature.Compared with the TiO₂thin films prepared by the traditional sintering method,for the films prepared by the VUV method as ETL of PSCs,the electron mobility and conductivity of ETL is improved,and the photogenerated charge interface recombination of ETL/perovskite is inhibited.Meanwhile,the prepared TiO₂films reduced the surface defects of the perovskite layer and improved the crystallinity of the perovskite layer.The PCE of the PSCs assembled by TiO₂ETL prepared by the VUV method reached 18.18%,which was 1.19%higher than that of the cells assembled by the traditional sintering method.（2）In order to improve the conductivity and interfacial energy alignment of the ETL of PSCs,a high-quality amorphous TiO₂film fabricated using vacuum UV light was combined with the Sn O₂thin film as ETL for PSCs.The experimental results and density functional theory（DFT）calculations show that there is a strong interaction between TiO₂and Sn O₂through the formation of Sn-O-Ti bonds,and the composite structure improves the electron mobility and conductivity of ETL.This interaction results in a well-aligned energy level between the composite ETL and the perovskite and reduces the interfacial defects between Sn O₂and the electrode substrate,which favors the transfer of photogenerated electrons.In addition,the introduction of amorphous TiO₂thin films resulted in the perovskite films with larger grains and lower density of defect states.PSC based on the composite ETL obtained 24.59%PCE and the stability of PSCs was improved.