All-inorganic CsPbI perovskite solar cells (PSCs) play a significant role in the new generation photovoltaic technology because of their unique optical band gap and excellent light absorption performance. However, the generation of defect states during the fabrication will cause serious non-radiative recombination and film degradation. Therefore, a new organic additive 4-Thioureidobenzoic acid (4-TBA) was introduced to decrease the defect density and optimize the device performance in this work. Thiourea group and carboxyl group in 4-TBA could not only be anchored on the film surface to passivate uncoordinated Pb defects as bilateral Lewis base, but also form the adjustable skeleton at the grain boundaries to fill Cs vacancies, support perovskite framework, boost the charge transfer and enhance the film crystallinity. Owning to the hydrophobicity of benzene ring structure of 4-TBA, the hydrophobic protective layer could be formed on the film surface and grain boundary to isolate the damage of external moisture to the device. Furthermore, with the release of residual stress in the film, the stability of device is substantially improved. Eventually, the 0.02 mol% 4-TBA based device prepared by one-step spin-coating method possesses an ultra-high power conversion efficiency (PCE) of 20.26%, which is one of the greatest efficiencies of all-inorganic CsPbI PSC at present. Surprisingly, after 1000 h of environmental stability test, the optimized device still maintains 95.6% of original efficiency without encapsulation, and the PCE attenuation is only 4.4%, showing excellent long-term stability.

中文翻译：

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CsPbI3钙钛矿太阳能电池双边路易斯碱可调骨架PCE超过20%且稳定性优越

全无机CsPbI钙钛矿太阳能电池（PSC）因其独特的光学带隙和优异的光吸收性能，在新一代光伏技术中发挥着重要作用。然而，制造过程中缺陷态的产生会导致严重的非辐射复合和薄膜退化。因此，在这项工作中，引入了一种新的有机添加剂4-硫脲基苯甲酸（4-TBA）来降低缺陷密度并优化器件性能。 4-TBA中的硫脲基和羧基不仅可以作为双边Lewis碱锚定在薄膜表面钝化不配位的Pb缺陷，而且可以在晶界处形成可调节的骨架来填充Cs空位，支撑钙钛矿骨架，增强电荷转移并增强薄膜的结晶度。由于4-TBA苯环结构的疏水性，可以在薄膜表面和晶界上形成疏水保护层，隔离外部湿气对器件的损害。此外，随着薄膜中残余应力的释放，器件的稳定性得到显着提高。最终，通过一步旋涂法制备的0.02 mol% 4-TBA基器件具有20.26%的超高功率转换效率（PCE），是目前全无机CsPbI PSC效率最高的器件之一。令人惊讶的是，经过1000 h的环境稳定性测试，优化后的器件在未封装的情况下仍然保持了原始效率的95.6%，PCE衰减仅为4.4%，表现出优异的长期稳定性。