Numerical Simulation Of Perovskite/Perovskite Tandem Solar Cells

Compared with the single-junction solar cell,tandem solar cell has a wider absorption spectrum,which is expected to break through the S-Q limit.In recent years,it has attracted the attention of many researchers,who have developed a lot of different types of tandem perovskite solar cells（PSCs）.Perovskite/perovskite tandem solar cells have the advantage of low cost and high efficiency,and the theoretical limit efficiency is up to 42%.Based on the above reasons,this thesis mainly focuses on the research and exploration of perovskite/perovskite tandem solar cells.Firstly,the device performance of single-junction MASn_0.5Pb_0.5I₃ solar cells is optimized.Furthermore,the all-inorganic perovskite（Cs Pb I₃,Cs Pb I₂Br,Cs Pb IBr₂）/MASn_0.5Pb_0.5I₃ tandem solar cells are simulated and optimized.The main contents are as follows:（1）The single junction MASn_0.5Pb_0.5I₃ PSC is studied,and its structure and performance are optimized.By comparing the external quantum efficiency,the net charge carrier generation rate and the carrier fermi level of different MASn_0.5Pb_0.5I₃ absorption layer thicknesses,the physical mechanism between the absorption layer thickness and the device performance is explored,and the absorption layer optimal thickness is 200 nm.Furthermore,the carrier transport layer（CTL）plays an important role in the process of electron and hole extraction and transport,so the influence of the CTL thickness and doping concentration on the device performance is investigated.The simulation results show that properly increasing the thickness of CTL can effectively improve the built-in electric field,so that the carrier can be extracted and transported more effectively,while too thick CTL will cause the device performance decline.In addition,appropriate doping of the CTL can significantly improve the device conductivity,resulting in higher fill factor（FF）and photoelectric conversion efficiency（PCE）.Finally,the MASn_0.5Pb_0.5I₃ PSC with short-circuit current density(J_sc)of30.38 m A/cm²and the PCE of 18.74%are obtained.（2）The perovskite/perovskite tandem solar cell with all-inorganic perovskite as the top cell absorption layer and narrow-bandgap perovskite MASn_0.5Pb_0.5I₃ as the bottom cell absorption layer is studied.In this part,four terminal and two terminal perovskite/perovskite tandem solar cells are studied simultaneously.In the four-terminal tandem device,the optimal perovskite layer thickness of top cell and bottom cell is 350 nm and 210 nm,respectively.Then,the CTL thickness is optimized to reduce the parasitic absorption and improve the device performance.In addition,the Li F anti-reflection layer is introduced on the top of the tandem solar cell to effectively improve the photon absorption rate of the four-terminal tandem cell.Finally,the PCE of the four-terminal all-perovskite tandem solar cell is 30.45%.Then,on the basis of four-terminal tandem cell,the two-terminal all-perovskite tandem cell is further studied.Here,narrow-bandgap perovskite MASn_0.5Pb_0.5I₃ is still used as the bottom cell absorption layer.However,all-inorganic perovskites with different halogen components（Cs Pb I₃,Cs Pb I₂Br and Cs Pb IBr₂）are used as the top cell absorption layer,and the optimization of photoelectric field distribution,parasitic absorption and current matching of sub-cells are adopted.Finally,the PCE of Cs Pb I₂Br/MASn_0.5Pb_0.5I₃tandem solar cells is up to 27.86%.