The α-to-δ phase transition and lattice defects pose significant challenges to the long-term stability of methylammonium (MA)/bromide (Br)-free formamidinium (FA)-based perovskite solar cells (PSCs). Here we propose an approach for bulk incorporating benzyl carbamimidothioate hydrochloride (BLSCl) to create 2D/3D perovskites without using MACl additive. This method effectively inhibits the α-to-δ phase transition and allows for improved modulation of crystallization within MA/Br-free FA-based PSCs. The BLS-induced multi-quantum-well structure significantly prevents water and oxygen corrosion. Moreover, BLS forms multiple hydrogen bonds and S–Pb coordination bonds with perovskite inorganic layers for modulating crystallization and passivating defects to create high-quality 2D/3D perovskite films. Consequently, the improved 2D/3D FA-based perovskite film possesses outstanding stability under harsh conditions (T = 200 °C, RH = 80%) without α-to-δ phase transition. The resultant PSCs achieved a remarkable efficiency of 25.96% (0.1 cm²). More importantly, an outstanding PCE of 24.54% (certified 23.94%) was attained for the 1.01 cm² device, which is the highest value for inverted MA/Br-free FA-based PSCs without MACl additive. Additionally, the optimized device demonstrates exceptional operational stability, with a T₉₆ value exceeding 1200 hours (T = 60 °C). These findings offer valuable insights into inhibiting phase transitions and optimizing crystallization processes in MA/Br-free FA-based PSCs.

中文翻译：

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高效稳定的无倒置 MA/Br 2D/3D 钙钛矿太阳能电池，通过 α 到 δ 相变抑制和结晶调制实现


α 到 δ 相变和晶格缺陷对无甲基铵 （MA）/溴化物 （FA） 基钙钛矿太阳能电池 （PSC） 的长期稳定性构成了重大挑战。在这里，我们提出了一种在不使用 MACl 添加剂的情况下批量掺入盐酸氨基甲酰氨基甲酸苄酯 （BLSCl） 以制备 2D/3D 钙钛矿的方法。该方法有效抑制了 α 到 δ 相变，并允许改进不含 MA/Br 的基于 FA 的 PSC 内结晶的调制。BLS 诱导的多量子阱结构显着防止了水和氧腐蚀。此外，BLS 与钙钛矿无机层形成多个氢键和 S-Pb 配位键，用于调节结晶和钝化缺陷，从而产生高质量的 2D/3D 钙钛矿薄膜。因此，改进的 2D/3D FA 基钙钛矿薄膜在恶劣条件下（T = 200 °C，RH = 80%）具有出色的稳定性，没有α到 δ 的相变。所得 PSC 实现了 25.96% （0.1 cm2） 的显着效率。更重要的是，1.01 cm2 器件获得了 24.54% 的出色 PCE（认证 23.94%），这是不含 MACl 添加剂的倒置无 MA/Br FA 的 PSC 的最高值。此外，优化后的器件表现出卓越的运行稳定性，T96 值超过 1200 小时 （T = 60 °C）。这些发现为抑制基于 MA/Br 的 FA 基 PSC 中的相变和优化结晶过程提供了有价值的见解。