Efficient Hole Transport Layer‐Free Mixed Sn–Pb Perovskite Solar Cells and Photodetectors via In Situ Dipole Engineering

ABSTRACT Mixed tin‐lead (Sn–Pb) perovskite solar cells (PSCs) have great potential for photovoltaics and infrared photodetector (PD) applications. However, their performance and reliability are severely limited by non‐radiative recombination, both within the perovskite bulk and at the interface between the perovskite and hole transporting layer (HTL). In HTL‐free architectures, the buried perovskite/ITO interface becomes the dominant extraction and recombination bottleneck, yet remains insufficiently engineered. Herein, we report an efficient HTL‐free mixed Sn–Pb optoelectronic device by introducing isoniazid (INH) into the perovskite film (FA 0.6 MA 0.3 Cs 0.1 Pb 0.5 Sn 0.5 I 3 ) to in situ form a dipole interface and establish a built‐in electric field, thereby suppressing the interface/bulk non‐radiative recombination and promoting hole extraction. The INH molecule can coordinate with Sn 2+ to modulate film crystallization, and the hydrazide group acts as a potent reducing agent, mitigating the Sn 2+ oxidation and passivating the defects. As a result, the optimized HTL‐free Sn–Pb PSCs achieved a champion power conversion efficiency (PCE) of 23.71%, with improved stability that retained 80% of their initial efficiency after 2250 h in an N 2 glovebox. Additionally, this strategy enabled high‐performance HTL‐free PDs with a remarkable specific detectivity beyond 10 14 Jones at 920 nm. This work provides a strategic pathway for developing efficient HTL‐free Sn–Pb perovskite optoelectronic devices.