The Preparation Of Perovskite Solar Cells And The Research On The Mechanism Of Carrier Recombination

As a clean,pollution-free and renewable energy source,solar energy has grown up to be a hot topic in the world.The emergence of perovskite solar cells in 2009 brought a bright future to address the energy crisis.Perovskite material has many unique advantages,such as adjustable band gap,higher light absorption,ease of fabrication,longer carrier diffusion length,two-dimensional conductivity characteristic and so on.The power conversion efficiency of the cell was only 3.8%at the beginning.Now its efficiency has exceeded 22%,which shows that the development potential of perovskite is huge.In perovskite solar cells,TiO₂ is the most widely used electron transport layer material because of its unique benefits.However,the material itself also has many defects.And these defects can significantly affect the performance of the cell.Research shows that doping the appropriate metal ions in TiO₂ can reduce the material defects and effectively improve the electron transport capacity of TiO₂.Therefore,this paper explores the influence of Fe³⁺doping on TiO₂ electron transport layer from a new perspective and also studies on the application of Fe³⁺doping in perovskite solar cells.This paper briefly reviews the development history and prospects of perovskite solar cells,and mainly focus on the preparation of perovskite solar cells with Fe³⁺-doped TiO₂ compact layer.In addition,the carrier recombination mechanism of the Fe³⁺-doped cells has been investigated in this thesis.The effects of Fe³⁺doping on the microstructure,optical and electrical properties of the TiO₂ layer are discussed.The main work of the thesis is as follows:（1）Fe³⁺is doped in TiO₂ solution to obtain different molar ratios of Fe³⁺-TiO₂solutions,and then a compact layer of Fe³⁺-doped TiO₂ is prepared by spray pyrolysis.XRD,XPS,SEM,V_TFLFL and UV-Vis absorption are utilized to compare the characteristics of TiO₂ films with different doping concentrations.It shows that 1 mol%Fe³⁺-doped TiO₂ film has the highest conductivity and the smallest defects.This is because Fe³⁺doping can reduce the oxygen vacancy defects in the TiO₂ film and improve the electron transport capability.（2）Fe³⁺-doped perovskite solar cells are prepared by an optimized one-step method.The crystallization,optical and electrical properties of perovskite films are observed by SEM,UV-Vis absorption and J-V curves.The result suggests that 1 mol%Fe³⁺-doped devices have the best performance（highest power conversion efficiency:18.60%,open circuit voltage:1.10 V,short-circuit current density:23.77 mA/cm²,fill factor:71.01%）.In other words,Fe-doped TiO₂ can effectively improve the cells’power conversion efficiency and carrier transport capability.（3）The high carrier recombination rate has a great negative influence on the efficiency and performance of the cell.In the experiment,the dark current,impedance spectrum,EQE and ideal factor are conducted to explore the carrier recombination mechanism in order to find an effectively way to suppress the carrier recombination rate.