Photocurrent Mapping And Charge Carrier Dynamics In Perovskite Devices

Through the continuous exploration of obtaining high-performance perovskite solar cells,researchers found that obtaining high-quality perovskite thin films is the key to obtaining high photoelectric conversion efficiency solar cells.The micro-nano structure of perovskite thin films,including grain size,shape,and grain boundaries,has a very large impact on the performance of titanite solar cells.Therefore,elucidating how and why perovskite micro-nanostructures alter local photophysical and photovoltaic performance is crucial for further improvement and optimization of perovskite solar cells.In this paper,through the combination of a time-resolved confocal PL microscope and a photocurrent detection module built in the laboratory,the relationship between the micro-nano space morphology characteristics,optoelectronic properties and photovoltaic parameters in perovskite solar cells is deeply discussed.The main research contents are as follows:（1）Design and build a system combining laser scanning confocal photocurrent imaging and PL imaging,and gradually improve the spatial resolution of photocurrent imaging.By using this technique,photocurrent imaging and in-situ PL intensity（lifetime）imaging tests of perovskite solar cells under practical working conditions were successfully achieved.（2）Imaging detection of photocurrent,PL intensity and PL lifetime in micro-nano space for two-dimensional（2D）layered perovskite solar cells under practical working conditions.It is found that in different regions of the same grain in the perovskite polycrystalline film,there is an obvious negative correlation between the photocurrent and the PL intensity and PL lifetime imaging,and the photovoltaic parameters are established on the micro-nano space scale.The correlation between morphologies provides theoretical guidance for the performance optimization of perovskite solar cells.（3）Through local photocurrent tests of MAPb I₃perovskite solar cells at different annealing temperatures,the effect of annealing temperature on the overall cell efficiency was observed.It is further illustrated that the lower annealing temperature（120°C）will cause a suitable amount of Pb I₂in MAPb I₃to precipitate and passivate the grain boundary,resulting in the enhancement of the photocurrent signal at the grain boundary.Higher annealing temperature（150°C）leads to excessive precipitation of Pb I₂in MAPb I₃,making grain boundaries the main recombination centers.（4）By using the combined technique of laser scanning confocal photocurrent imaging and PL imaging,local photocurrent,PL intensity and PL lifetime imaging are directly realized in FAPb I₃perovskite solar cells under working conditions.It is shown that larger perovskite grains may have fewer defects,leading to higher charge collection efficiency,and the optimal grain size was found to be≥2μm.This result demonstrates that precise control over the growth of perovskite microstructures can further improve the performance of perovskite solar cells.