Root cause for the difference in photovoltaic parameters of perovskite solar cells prepared by one- and two-step processes

Benefiting from good solubility of metal halide perovskites, low-temperature solution processes (including one- and two-step spin-coating) have become the most common approach for perovskite solar cells (PSCs). However, one confusing issue is that what are specifically effective strategies for the one-step process may not be applicable for the two-step process, and vice versa. Herein, the PSCs with the same perovskite composition and device configuration were prepared by one- and two-step processes, respectively. The results indicated that high performance PSCs with comparable power conversion efficiency over 22% were achieved by both methods, while the detailed photovoltaic parameters varied greatly depending on the one- or two-step process. Compared to the one-step counterpart, the two-step processed PSCs exhibit lower open-circuit voltage and fill factor, but superior short-circuit current, which was in-depth interpreted in terms of the crystalline growth mode, optical properties, defect types, and carrier transport mechanisms related to a perovskite film surface (including a top and a bottom surface). Understanding the root cause for such differences would be central toward identifying what is really crucial for further producing high performance PSCs. Published under an exclusive license by AIP Publishing.