Cs₂AgBiBr₆ double perovskites are considered potential alternatives to lead-based perovskites for solar cell applications owing to their advantages of stability and non-toxicity. However, the disordered arrangement of Ag/Bi octahedra leads to the formation of self-trapped excitons (STEs) and hinders carrier transport, which is a severe problem in planar solar cells due to inferior charge extraction to mesoporous solar cells. Herein, we employ ethoxylated polyethylenimine (PEIE) to regulate the growth of Cs₂AgBiBr₆ films by sandwiching it between an SnO₂ electron transport layer and a perovskite layer. On the one hand, the introduction of PEIE delays the growth of Cs₂AgBiBr₆ and improves the ordering extent of the Ag/Bi octahedra. This inhibits the formation of STEs and facilitates carrier transport, which profoundly boosts the short-circuit current density. On the other hand, PEIE modulates the energy level of the SnO₂ electron transport layer to match that of Cs₂AgBiBr₆, which reduces the open-circuit voltage loss. Consequently, the power conversion efficiency (PCE) of the planar solar cell increases by 250% after PEIE modification from 0.59% to 1.52%. In addition, the PEIE-decorated device maintains over 90% of its initial PCE for 30 days under ambient conditions, demonstrating good environmental stability.

中文翻译：

---

Cs2AgBiBr6 双钙钛矿在 PEIE 修饰的 SnO2 上有序生长，用于高效平面太阳能电池

Cs ₂ AgBiBr ₆双钙钛矿由于其稳定性和无毒性的优点而被认为是太阳能电池应用中铅基钙钛矿的潜在替代品。然而，Ag/Bi八面体的无序排列导致自陷激子（STE）的形成并阻碍载流子传输，这在平面太阳能电池中是一个严重的问题，因为电荷提取能力比介孔太阳能电池差。在此，我们采用乙氧基化聚乙烯亚胺（PEIE）通过将其夹在SnO ₂电子传输层和钙钛矿层之间来调节Cs ₂ AgBiBr ₆薄膜的生长。一方面，PEIE的引入延缓了Cs ₂ AgBiBr ₆的生长，提高了Ag/Bi八面体的有序程度。这抑制了 STE 的形成并促进载流子传输，从而极大地提高了短路电流密度。另一方面，PEIE调节SnO ₂电子传输层的能级以匹配Cs ₂ AgBiBr ₆的能级，这减少了开路电压损失。因此，PEIE改性后平面太阳能电池的功率转换效率（PCE）提高了250%，从0.59%提高到1.52%。此外，PEIE装饰的器件在环境条件下30天仍保持其初始PCE的90%以上，表现出良好的环境稳定性。