Perovskite solar cells have become a research hotspot in the field of new energy due to the excellent performance and potential in application, but it still displays some disadvantages such as high defect density and poor stability. In this study, L-arginine, a small molecule of organic matter, was doped into the perovskite precursor solution by comparing the doping effects of various amino acids, and the perovskite solar cells were prepared by the two-element and two-step preparation method. The test results show that L-arginine doping improves the photoelectric performance of the device, and the photoelectric efficiency increases from 18.81% to 21.86%. L-arginine reduces the nonradiative recombination of carriers and increases the average carrier life by reducing the defect density of perovskite layer from 4.83×10 16 cm -1 to 3.45×10 16 cm -1 . In addition, the perovskite grain size increases, grain boundaries decrease, the light absorption ability and stability of the film are enhanced, and the hysteresis effect was also suppressed. Improvement of the photovoltaic performance is due to the passivation of defects by the interaction of various groups of L-arginine with perovskite materials. This study provides a reference method of the optimization of perovskite solar cells.

Defects of perovskite (PVK) films are one of the main obstacles to achieving high‐performance perovskite solar cells (PSCs). Here, the authors fabricated highly efficient and stable PSCs by introducing prolinamide (ProA) into the PbI2 precursor solution, which improves the performance of PSCs by the competitive crystallization and efficient defect passivation of perovskite. The theoretical and experimental results indicate that ProA forms an adduct with PbI2, competes with free I− to coordinate with Pb2+, leads to the increase of the energy barrier of crystallization, and slows down the crystallization rate. Furthermore, the dual‐site synergistic passivation of ProA is revealed by density functional theory (DFT) calculations and experimental results. ProA effectively reduces non‐radiative recombination in the resultant films to improve the photovoltaic performance of PSCs. Notably, ProA‐assisted PSCs achieve 24.61% power conversion efficiency (PCE) for the champion device and the stability of PSCs devices under ambient and thermal environments is improved.