Research On Performance Optimization Of Tin-based Perovskite Solar Cells

Perovskite solar cells（PSCs）is developing very rapidly and the power conversion efficiency（PCE）has reached 25.5%.However,most of the current high-efficiency PSCs use lead-based perovskite materials as the light-absorbing layer,cause environmental pollution and endanger personal safety.Among the lead-free PSCs,Sn-based PSCs have become the most promising lead-free PSCs today due to their excellent electrical and optical properties such as high absorption coefficient,low exciton binding energy,and high charge carrier mobility.However,Sn-based PSCs face two very important problems:low efficiency and poor stability.This paper mainly studies the effects of interface modification,the use of additives and solvent engineering on the performance of FASn I₃ Sn-based PSCs.The specific research work is as follows:（1）By doping different concentrations of Cs I or Cs Br in the hole transport layer Poly（3,4-ethylenedioxythiophene）PEDOT:PSS,enhance the hole extraction of PEDOT:PSS,which energy levels are more favorable between hole transport layer and perovskite layer.Moreover,after Cs I or Cs Br modifification,the defects of the perovskite films can be passivated after doping,which optimizes the overall performance of Sn-based PSCs.The performance of the devices with doping concentratons of 0 mg/m L、2.5 mg/m L、5.0 mg/m L、7.5 mg/m L was studied.When the doping concentration of Cs I and Cs Br is 5.0 mg/m L,the PCE of the device is the highest,3.59%and 3.46%respectively.（2）By doping the nitrogen-containing heterocyclic organic compound melamine to the perovskite light-absorbing layer FASn I₃,the short-circuit current density of the device is mainly increased,which leads to an increase in the PCE of the device.The effects of doping of 0、0.5%、1.0%and 1.5%on the surface morphology and the performance of Sn-based PSCs devices were systematically studied.The study found that the surface morphology of the perovskite film is the best when the doping amount is 1.0%,and the device performance is the best,with a PCE of 4.31%.The encapsulated devices can maintain 86%of the initial PCE when stored in a nitrogen-filled glovebox for 400 hours.（3）By doping small organic molecules 2,3,5,6-tetraflfluoro-7,7,8,8-tetracyanoquinodimethane（F4TCNQ）to the anti-solvent to passivate the Sn-based perovskite grain boundary defects and inhibit carrier recombination,chlorobenzene was used as the anti-solvent to compare the doping concentration of F4TCNQ to 0 mg/m L、0.01 mg/m L、0.03 mg/m L、0.05 mg/m L Sn-based perovskite film surface morphology,crystallinity and device performance.As the doping concentration is 0.03 mg/m L,obtain the optimazet performance of the device,and the PCE is increased from 3.28%to 4.47%.The encapsulated devices can still maintain 84%of the initial PCE when stored in a nitrogen-filled glovebox for 400 hours.