A processing window exists during the transition between film formation and the annealing step in the two-step method employed for the fabrication of FAPbI₃ perovskite solar cells, independent of whether the aim is to produce a batch of small-area or large-area devices. A significant variance in the power conversion efficiencies of perovskite devices, resulting from different processing windows, leads to a marked decrease in device reproducibility. To investigate the changes occurring within the perovskite wet film during the processing window, this study utilized nitrogen protection packaging technology to monitor the crystallization process of the perovskite wet film outside the glove box. The observation indicated non-uniform intermediate-phase reaction rates. The incorporation of 3-cyanopyridine into the two-step method decelerated the crystallization kinetics of the perovskite wet film, suppressing the formation of δ-FAPbI₃. Such modification expanded the processing window time, enabling the preparation of perovskite films with superior crystallinity and minimal defects. The n-i-p type perovskite solar cells exhibited a power conversion efficiency (PCE) of 25.12%. The findings demonstrate that this modification method effectively extends the processing window time of the two-step method, leading to the fabrication of perovskite devices with optimal performance and high repeatability. This represents a novel strategy for the batch production of perovskite devices and the manufacturing of large-area perovskite films.

In organic solar cells, the singlet and triplet excitons dissociate into free charge carriers with different mechanisms due to their opposite spin state. Therefore, the ratio of the singlet and triplet excitons directly affects the photocurrent. Many methods were used to optimize the performance of the low-efficiency solar cell by improving the ratio of triplet excitons, which shows a long diffusion length. Here we observed that in high-efficiency systems, the proportion of singlet excitons under linearly polarized light excitation is higher than that of circularly polarized light. Since the singlet charge transfer state has lower binding energy than the triplet state, it makes a significant contribution to the charge carrier generation and enhancement of the photocurrent. Further, the positive magnetic field effect reflects that singlet excitons dissociation plays a major role in the photocurrent, which is opposite to the case of low-efficiency devices where triplet excitons dominate the photocurrent.