The Investigation Of Modified Electron Transport Layer In Perovskite Solar Cells

Energy shortage and environmental pollution are the two major challenges which human are confronted with.Therefore,scientists all over the word are looking for new and clean energy to replace the traditional non-renewable energy.As we all know,the solar energy is inexhaustible and clean.And the most common use of solar energy is converting sunlight into electrical energy by solar cells.Presently,silicon-based solar cells are the most widely used,but the expensive cost and the environmental pollution are restricting the development of solar cells.So,it is important to find new solar cells that are provided with the lower manufacturing cost,simple production process and environment-friendly.Since the first report of perovskite in the field of solar cells by Miyasaka and co-workers in 2009,the perovskite solar cells?PSCs?have attracted tremendous attention.And the power conversion efficiency?PCE?of PSCs has reached a record of over 21.0%for several years.Typical PSCs are usually consist of transport anode layer fluorine-doped tin oxides?FTO?or indium tin oxides?ITO?),electron transport layer?ETL?,perovskite as a light sensitive layer,hole transport layer?HTL?,and mental cathode.In particular,ETL plays an important role in achieving a high PCE since it can provide a transport pathway for light-induced electrons from perovskite to photoanode and avoid recombination with holes generated in the perovskite.Traditionally,TiO₂ thin film is chosen as ETL widely due to its suitable conductivity and stability.However,there are some defects in TiO₂,would serve as recombination centers for electrons and holes,which can deteriorate the PCE performance of PSCs.Meanwhile,the quality of perovskite film is also important due to it can affect the transportion of electron-hole and the absorption of visible light.Therefore,to seek other appropriate N type semiconductor materials as electron transport layer or to modify TiO₂and the appropriate methods for fabricating perovskite film has become the present popular topic.Based on the above problems,we modified the surface of TiO₂ by some methods.We found the cadmium sulfide?CdS?have been used widely in quantum dot solar cells due to its better electron mobility and light stability,so we introduced the CdS to modify the surface of TiO₂,investigating whether the performance of PSCs are improved.We also modified TiO₂ by hydrogenation to explore if the performance were enhanced.Additionly,we explore a suitable simple preparation of perovskite thin films with high quality.This paper mainly includes the following several parts:Firstly,it points out the development?structure and working principle of PSCs concisely and this part also elaborated the background of the selected topic and the main research content of this paper.Secondly,we explored one-step and two-step method to manufacture perovskite film.The high perovskite film was obtained by a simple two-step vapor-assisted method.Thirdly,we deposited the CdS on TiO₂ substrate by microwave-assisted hydrothermal method,investigating the effects of different thickness on the PSC performance.By optimizing the thickness of CdS,compared to a PCE of 10.31%for the reference TiO₂ PSCs without the CdS layer,largely increased PCE is achieved for CdS based PSCs and the champion efficiency is as high as 14.26%,mainly reflected in the open circuit voltage and short circuit current.Fourthly,we modified TiO₂ by hydrogenation.By optimizing the hydrogenation temperature,compared to a PCE of 9.45%for the reference TiO₂ PSCs,largely increased PCE is achieved for hydrogenated PSCs and the champion efficiency is as high as 13.15%,mainly reflected in the open circuit voltage and fill factor.Fifthly,it figures out the summary and prospect of this paper.