Preparation Of Perovskite Thin Films By Gas-assisted Solution Method And Research On Device Performance

The characteristics of high absorption coefficient,bipolar transport characteristics,adjustable band gap,low production cost,and high photoelectric conversion efficiency have made perovskite solar cells have received extensive attention from researchers in recent years,and their photoelectric conversion efficiency records have reached 25.5%.However,the industrial production of perovskite solar cells still has problems in large-scale preparation and stability.In this paper,the gas phase reaction process in the gas phase assisted solution method is optimized,and the stepwise evaporation methylamine iodide(MAI)process is developed to improve the photoelectric conversion efficiency(PCE)and stability of the device,and the stepwise evaporation is studied.The mechanism of perovskite growth in the MAI process.On this basis,the optimized gas-phase auxiliary solution method is used to control the halide anion composition in the perovskite,thereby adjusting the band gap,and applying it to the trial preparation of the perovskite-Sb₂Se₃ tandem battery.The main research contents of this paper are as follows:(1)According to the optimization of the gas phase reaction process in the gas phase assisted solution method,the evaporation of MAI is divided into two stages:evaporation under normal pressure and vacuum(pressure in the chamber is about 1.5 Pa).The results show that the best and average PCE of the device prepared by the optimized process reached 18.08%and17.06%,respectively,while the reference best device was only 14.80%and12.89%.At the same time,the stability of the device has also been improved.In an environment of about 30%humidity,the PCE of the device prepared by the optimized process can still maintain 70%of the initial value,while the reference device is only 40%.The improvement of device performance is because during the stepwise evaporation of MAI,the first step of MAI evaporation is relatively slow,which can promote the MAI vapor to enter more inside the PbI₂ film,and form perovskite seeds inside the PbI₂,which promotes more reaction.Complete,which is beneficial to reduce the defect state density of the perovskite film and improve battery performance.(2)Using the optimized step-by-step gas-assisted solution method,PbI₂ solution was doped with different concentrations of PbBr₂ to change the composition of the perovskite film,and a large area was prepared.At the same time,through band gap adjustment,try to prepare perovskite-Sb₂Se₃ tandem battery.The results showed that after doping with 0.7 M Br,the best PCE reached 18.5%,which was 2.3%higher than that of undoped,and the stability was also improved.PCE was exposed to 30%humidity after 500 hours of continuous illumination.It can still maintain 87%of the initial value.In large-area preparation,the best PCE after Br doping is12.65%,which is slightly higher than that without doping.The improvement of device performance is due to the slower growth rate of perovskite crystals after the addition of Br,which makes the crystal grains larger,thereby reducing the non-radiative recombination of carriers.However,the preparation effect of the perovskite-Sb₂Se₃ tandem battery is not good.It is speculated that during the preparation process,the lower film will be affected by the temperature during the preparation of the upper film,resulting in a significant decrease in performance.