We investigated the doping effect of bulky organic cations with ethylenediammonium diiodide (EDAI₂) and butylammonium iodide (BAI) as additives to passivate surface defects, to control the film morphology and to improve the crystallinity for inverted planar FASnI₃ perovskite solar cells. The addition of BAI altered significantly the orientation of crystal growth and improved the connectivity of the crystal grains, but the existence of pinholes in the surface of the pristine FASnI₃ films was unavoidable; this effect impeded further improvement of the device performance (PCE 5.5%), which is nevertheless superior to that of a pristine FASnI₃ film (PCE 4.0%). The addition of EDAI₂ had the effect of curing the pinhole problem, passivating the surface defect states, preventing Sn²⁺/Sn⁴⁺ oxidation and inducing slow relaxation of the crystal structure. In the presence of the EDAI₂ additive (1%), the FASnI₃ device attained the best initial efficiency, 7.4%, and the device performance continuously increased as a function of duration of storage; the maximum PCE, 8.9%, was obtained for a device stored in a glove box for over 1400 h with only slight degradation for storage beyond 2000 h. The observed slow passivation of surface defects and relaxation of crystal strain were verified with X-ray diffraction, X-ray photoelectron spectroscopy and photoluminescence decay techniques.

中文翻译：

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慢速表面钝化和晶体松弛与添加剂一起使用，可改善锡基钙钛矿太阳能电池的器件性能和耐用性†

我们研究了乙二胺二碘化铵（EDAI ₂）和丁基碘化铵（BAI）作为添加剂钝化表面缺陷，控制膜的形态并提高倒置平面FASnI ₃钙钛矿型太阳能电池的结晶度对大体积有机阳离子的掺杂效果。BAI的添加显着改变了晶体生长的方向并改善了晶粒的连通性，但是原始FASnI ₃膜表面不可避免地存在针孔；这种效果阻碍了器件性能的进一步提高（PCE 5.5％），但仍优于原始的FASnI ₃膜（PCE 4.0％）。EDAI _2的添加具有解决针孔问题，钝化表面缺陷状态，防止Sn ²⁺ / Sn ⁴⁺氧化并引起晶体结构缓慢弛豫的作用。在存在EDAI ₂添加剂（1％）的情况下，FASnI ₃器件获得了7.4％的最佳初始效率，并且器件性能随着存储时间的延长而不断提高。对于置入杂物箱中超过1400小时的设备，其最大PCE为8.9％，而对于超过2000小时的存储，则仅有很小的降解。X射线衍射，X射线光电子能谱和光致发光衰减技术证实了观察到的表面缺陷的缓慢钝化和晶体应变的松弛。