Dual Effects of Slow Recrystallization and Defects Passivation Achieve Efficient Tin-Based Perovskite Solar Cells with Good Stability Up to One Year

Tin-based perovskite solar cells (TPSCs) have become a star candidate in lead-free perovskite cells due to their excellent optoelectronic properties and low toxicity. However, there are a lot of problems such as uncontrollable crystallizationprocess, easy oxidation of Sn²⁺ and high defect density have not been completely resolved in TPSCs. Here, the thiourea (TU) and amidine thiourea (ASU) are added into the perovskite precursor to regulate the microstructure, inhibit the oxidation of Sn²⁺ and promote charge transfer. The characterization results demonstrate that the TU additive can not only improve the micrograph, crystallinity and antioxidant, but also significantly induce recrystallization and passivate trap states. Thus, the TPSCs with TU (TU-modified TPSCs) show a significantly higher power conversion efficienc (PCE) and better stability than those of the TPSCs with ASU (ASU-modified PSCs) and reference TPSCs. After stored in N₂ atmosphere for 8 months, the unencapsulated TU-modified PSCs achieve a champion PCE of 10.9% with an open-circuit voltage of 0.79 V. Furthermore, the unsealed TU-modified PSCs can maintain 115% of its initial efficiency after stored in N₂ atmosphere for one year. This is the longest lifetime of unencapsulated pure TPSCs in N₂ atmosphere.