Chlorobenzene solvent annealing of perovskite thin films for improving efficiency and reproducibility of perovskite solar cells

In recent years, metal halide perovskite solar cells have developed rapidly, with certified power conversion efficiency of over 25% for single-junction solar cells. However, these devices still face challenges such as low efficiency and poor reproducibility, where the quality of the absorbing layer is an essential factor affecting the performance of perovskite solar cells. The triple-cation perovskite thin films prepared based on the two-step method have residuals of lead iodide and a large number of grain boundaries and other defects, leading to the charge carrier recombination and thus to degrade the cell photovoltaic performance. Solvent annealing is a method to improve the performance of perovskite solar cells and has been proven to improve the efficiency and reproducibility. Herein, this work introduced chlorobenzene solvent annealing during the preparation of the organic layer of the perovskite thin film. The results show that the treated perovskite film have increased the grain size of the perovskite thin film and meanwhile reduced its defects. At the same time, this treatment significantly reduced the residual lead iodide in the perovskite film, resulting in an improvement in the reproducibility of the devices. Moreover, this treatment also contributed to enhance the specific gravity of radiative recombination and to prolong the carrier lifetime in the film, thus improving the efficiency of the solar cell. As a result, the cell efficiency and reproducibility were improved, where the average and the highest efficiencies were increased by 16.38% and 5.87%, respectively, compared to the perovskite solar cells prepared without the chlorobenzene solvent annealing treatment. Therefore, this work provides a promising idea for improving the quality of perovskite films and further optimizing the efficiency of perovskite solar cells.