Interface Recombination Inhibition And Charge Separation Enforcement For Wide-Bandgap Perovskite Solar Cells

Metal halide perovskite solar cells have attracted wide attention from researchers in recent years due to their low cost,high efficiency,continuously adjustable bandgap,and solution processability.Wide-bandgap perovskite solar cells with a bandgap greater than 1.7 e V can be stacked with silicon cells,copper indium gallium selenide cells,and narrow bandgap perovskite cells to fabricate tandem cells,which are expected to exceed the Shockley-Queisser efficiency limit and maximize solar energy utilization.As the top sub-cell of tandem cells,wide-bandgap perovskite cells can capture high-energy photons and generate high photo-voltage,making a significant contribution to the performance of tandem cells.Therefore,it is crucial to develop highly efficient wide-bandgap perovskite solar cells,explore defect passivation strategies and charge separation mechanisms of wide-bandgap perovskites to reduce non-radiative recombination and photo-voltage loss,and suppress photo-induced phase segregation.In this thesis,mixed cationic mixed halide wide-bandgap perovskite solar cells with a bandgap of 1.79 e V and a composition of Cs_0.15FA_0.8MA_0.05Pb(I_0.6Br_0.4)₃ are developed.Subsequently,three alkali metal chlorides,KCl,Rb Cl,and Cs Cl,are employed for modifying the interface between Sn O₂ electron transport layer and wide-bandgap perovskite layer to enhance charge separation,suppress non-radiative recombination,and improve the photovoltaic performance of the cell.Absorption spectra and fluorescence analysis confirms that the alkali metal chloride modification not only improves the charge extraction at wide-bandgap perovskite interface,but also passivates the defect states of perovskite,suppresses non-radiative recombination,and inhibits photo-induced phase segregation to some extent.Photovoltaic responses reveal that alkali metal chloride modification enhances open-circuit voltage and fill factor remarkably,and improves device stability.The device modified with KCl achieved a power conversion efficiency of 18.4%under a 100 m W cm^-2 simulated solar irradiation.The performance of the KCl modifed wide-bandgap perovskite cells is further improved by modifying the interface between wide-bandgap perovskite and hole transport layer with a composite passivator（4-tert-butyl-phenylmethylammonium iodide and guanidinium iodide）.Spectral analyses and electrochemical measurements show that such double-interface passivation further suppresses the defect states and non-radiative recombination.Impedance analyses show that the double-interface passivation could inhibit the long-range migration of mobile ions,thereby reducing the interface recombination loss.Photovoltaic responses show that the double-interface passivation improves open-circuit voltage significantly.The device with double-interface passivation yields an open-circuit voltage of 1.33 V,which is 80m V and 130 m V higher than the KCl-passivated and pristine conterparts,respectively.It indicates an apparent reduction of photovoltage loss.The wide-bandgap perovskite device with double-interface passivation achieves a power conversion efficiency of20.1%under simulated solar light irradiation with an intensity of 100 m W cm^-2.This double-interface passivation strategy provides a new protocol for fabricating high-efficiency wide-bandgap perovskite solar cells.