Monolithic perovskite silicon tandem solar cells can overcome the theoretical efficiency limit of silicon solar cells. This requires an optimum bandgap, high quantum efficiency, and high stability of the perovskite. Herein, a silicon heterojunction bottom cell is combined with a perovskite top cell, with an optimum bandgap of 1.68 eV in planar p–i–n tandem configuration. A methylammonium‐free FA_0.75Cs_0.25Pb(I_0.8Br_0.2)₃ perovskite with high Cs content is investigated for improved stability. A 10% molarity increase to 1.1 m of the perovskite precursor solution results in ≈75 nm thicker absorber layers and 0.7 mA cm⁻² higher short‐circuit current density. With the optimized absorber, tandem devices reach a high fill factor of 80% and up to 25.1% certified efficiency. The unencapsulated tandem device shows an efficiency improvement of 2.3% (absolute) over 5 months, showing the robustness of the absorber against degradation. Moreover, a photoluminescence quantum yield analysis reveals that with adapted charge transport materials and surface passivation, along with improved antireflection measures, the high bandgap perovskite absorber has the potential for 30% tandem efficiency in the near future.

中文翻译：

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具有高带隙钙钛矿吸收体的25.1％高效整体钙钛矿硅串联太阳能电池

整体钙钛矿硅串联太阳能电池可以克服硅太阳能电池的理论效率极限。这需要钙钛矿的最佳带隙，高量子效率和高稳定性。在本文中，硅异质结底部电池与钙钛矿顶部电池组合在一起，在平面p–i–n串联配置中的最佳带隙为1.68 eV。研究了具有高Cs含量的无甲铵FA _0.75 Cs _0.25 Pb（I _0.8 Br _0.2）₃钙钛矿的稳定性。钙钛矿前体溶液的摩尔浓度增加10％至1.1 m会导致吸收层厚度增加约75  nm和0.7 mA cm ^-2更高的短路电流密度。使用优化的吸收器，串联设备可达到80％的高填充率和高达25.1％的认证效率。未封装的串联设备在5个月内效率提高了2.3％（绝对值），显示了吸收器抗降解的坚固性。此外，光致发光量子产率分析表明，采用合适的电荷传输材料和表面钝化技术以及改进的减反射措施，高带隙钙钛矿吸收剂在不久的将来有可能实现30％的串联效率。