Effect Mechanism Of Lewis Acid-base Adducts On PCE Properties Of Inorganic Cs-based PSC

Black-phase all-inorganic Cs Pb I₃thin films have attracted a lot of attention in the field of photovoltaics because of their excellent chemical stability,thermal stability,light stability and high PCE,making them potential candidates for commercial chalcogenide solar cells at present.In recent years,the PCE of Cs Pb I₃ solar cells（PSC）has rapidly increased from the first reported 2.9%to 21%,and the PCE between organic-inorganic hybrid solar cells has been narrowed;meanwhile,inorganic materials are more stable than organic materials in high-temperature and high-moisture environments,thus making them more attractive in commercial application prospects.Cs Pb I₃ has a suitable band gap（≈1.70 e V）and can be used as the top cell of tandem Perovskite/silicon stacked cells.Perovskite/silicon stacked cells,as a new device structure,have been gaining breakthroughs in efficiency and are now certified to have an efficiency of 31.3%,far exceeding that of conventional silicon cells.However,the I-rich chalcogenide thin film material is highly sensitive to water molecules and prone to phase change,which seriously affects its further application.To this end,in this paper,we used halogen atoms（Br,Cl）to supplant the components of Cs Pb I₃ thin films to construct all-inorganic Perovskite solar cells based on Cs Pb I_2.75Br_0.249Cl_0.01（Cs Pb Th₃）thin films,and engineered Cs Pb I_2.75Br_0.249Cl_0.01 by using Lewis acid-base adducts as additives（Cs Pb Th₃）all-inorganic solar cells were modified in order to improve cell PCE and cell stability.The main studies in this thesis are as follows.（1）The modification of Cs Pb Th₃ thin films was achieved by regulating the cell nucleation and growth rate of Cs Pb Th₃ thin films by adjusting the different doping concentrations of Cs PF₆.The morphology,physical phase and structure of Cs PF₆-Cs Pb Th₃composite films were characterized by XRD,XPS,SEM and AFM,and combined with the J-V test results to reveal the mechanism of coordination of Cs PF₆ with vacant I to achieve the purpose of passivation of defects to improve the PCE.The experiments show that the stability and PCE of Cs Pb Th₃ films can be effectively improved by using Cs PF₆,and the PCE of the films shows a trend of increasing and then decreasing with the increasing doping concentration of Cs PF₆.When the doping concentration of Cs PF₆is 0.6 mg/m L,the prepared Cs Pb Th₃ films have uniform cell orientation and large particle size,and the PSC performance based on this film is optimal,with the photoelectric conversion efficiency（PCE）,open circuit voltage(V_OC),short circuit current density(J_SC)and fill factor（FF）of18.4%,1.1 V,20.08 m A cm^-2 and 82.6%,while the PCE of the untreated Cs Pb Th₃ film was only 17.89%.（2）Simulation calculations using DFT and combined with experimental results were performed to investigate the binding mechanism of the uncoordinated anions PF₆^-,BF₄^-and I ions with the undercoordinated Pb²⁺to achieve passivation of I vacancy defects.On this basis,Lewis acid-base adduct strategy（LABAs）was employed to introduce N-methylpropyl piperidine（NPMP⁺）and PF₆^-to act together on Cs Pb Th₃ chalcogenide layer to regulate the crystallization and thus improve the stability of chalcogenide films.It is shown that PF₆^-is more effective than BF₄^-in binding to Pb²⁺for passivation,thus providing a good suppression of I defects.In addition,the PCE of the LABAs-Cs Pb Th₃ films treated with NPMP⁺and PF₆^-can reach 19.02%of the devices under standard solar illumination(100m W cm^-2),maintain 76%of the initial efficiency after aging in air for 60 days,and still show good phase stability after 250 days in air.