Low-band-gap tin (Sn)-lead (Pb) perovskites are a critical component in all-perovskite tandem solar cells (APTSCs). Current state-of-the-art Sn-Pb perovskite devices exclusively use poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) as the hole-transport layer (HTL) but suffer from undesired buried-interface degradation. Here, we show that the deprotonation of the –SO₃H group in PSS is the root cause of the interface degradation due to its low acid dissociation constant (pK_a), leading to acidic erosion and iodine volatilization in Sn-Pb perovskites. We identify that HTL featuring the carboxyl (–COOH) group with a higher pK_a, such as poly[3-(4-carboxybutyl)thiophene-2,5-diyl] (P3CT), can suppress deprotonation and strengthen the interface, mitigating the buried-interface degradation. Motivated by established P3CT modification, we introduce Pb doping to P3CT to increase its work function and reduce interfacial energy loss. We fabricate APTSCs with a champion efficiency of 27.8% and an operational lifetime of over 1,000 h, with 97% retaining efficiency under maximum power point tracking.

低带隙锡 (Sn)-铅 (Pb) 钙钛矿是全钙钛矿串联太阳能电池 (APTSC) 的关键组件。目前最先进的 Sn-Pb 钙钛矿器件专门使用聚（3,4-乙撑二氧噻吩）-聚（苯乙烯磺酸）（PEDOT:PSS）作为空穴传输层（HTL），但会遭受不需要的埋入界面退化。在这里，我们发现PSS中-SO ₃ H基团的去质子化是界面降解的根本原因，因为它的酸解离常数（p Ka _）较低，导致Sn-Pb钙钛矿中的酸性侵蚀和碘挥发。我们发现具有较高 p Ka_的羧基（-COOH）基团的 HTL ，例如聚[3-（4-羧丁基）噻吩-2,5-二基]（P3CT），可以抑制去质子化并增强界面，减轻埋入界面的退化。在已建立的 P3CT 改性的推动下，我们将 Pb 掺杂引入到 P3CT 中，以提高其功函数并减少界面能量损失。我们制造的 APTSC 的冠军效率为 27.8%，使用寿命超过 1,000 小时，在最大功率点跟踪下保持效率为 97% 。