Study On Perovskite Solar Cells Based On Lewis Base Passivation

Organic and inorganic hybrid perovskite is developing rapidly.The adjustable band gap of perovskite（PVSK）material makes it widely used in laser,light-emitting diode,solar cell and photodetector and so on.The photoelectric conversion efficiency of perovskite solar cells（PSCs）has broken through from 3.8%to 25.7%in more than a decade,surpassing that of polysilicon solar cells with decades of development history.This is due to the excellent inherent characteristics of PVSK,including high absorption coefficient,high carrier mobility,long carrier diffusion length,and direct band gap.However,a variety of defects caused by the ionic crystal properties of PVSK and the interface generated by the multilayer structure of PSCs both lead to the accumulation and recombination of carriers,which reduces the device performance and stability of PSCs.Therefore,passivation of the defects in the bulk phase and interface of PSCs to achieve high efficiency and stability of PSCs is an important topic in the field of perovskite photovoltaic materials in recent years.1.Using benzo[d]isothiazol-3（2H）-one 1,1-dioxide（OBS）as additive,perovskite precursor formulated with(FA_0.95Cs_0.05Pb I₃)_0.975（MAPb Br₃）_0.025was introduced.The optimal concentration of OBS was determined to be 0.6 mg/m L by photovoltaic performance parameters of the device.Subsequently,the FAMACs ternary-cation PSCs films or devices without OBS doping were taken as the control group,and the PSCs films or devices containing 0.6 mg/m L OBS were taken as the experimental group.A series of characterizations of perovskite films and devices were performed.The hydrogen bond and coordination bond interactions between OBS and perovskite were revealed by Fourier infrared spectroscopy（FTIR）and X-ray photoelectron spectroscopy.The effects of OBS on device performance were revealed by various characterization,including X-ray diffraction,UV-VIS spectroscopy,electrochemical impedance spectroscopy,etc.The OBS-treated device achieved a 23.26%high efficiency,while the control device showed only 21.60%PCE.2.Use benzoic acid and its derivatives:Benzoic acid（BA）,p-bromobenzoic acid（4-BBA）and p-methythiobenzoic acid（4-MTBA）were dissolved in isopropyl alcohol and coated on the upper surface of perovskite film with formula of(FA_0.9Cs_0.07MA_0.03Pb(I_0.92Br_0.08)₃as passivation layer.The optimal concentration and spin coating mode of BA,4-BBA and 4-MTBA were determined by the photovoltaic performance parameters of the device.The influence of benzoic acid functional group on carboxyl group was determined by theoretical calculation and experiment,and the dipole moment direction of passivator was adjusted.Finally,4-MTBA was determined as the optimal passivator.The 4-MTBA passivated PSCs obtained a champion efficiency of 23.16%,and the PSCs devices still showed more than 90%of the original efficiency after 2200 h placement in the air stability test.