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_0.6MA_0.3Cs_0.1Pb_0.5Sn_0.5I₃) 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 Sn²⁺ to modulate film crystallization, and the hydrazide group acts as a potent reducing agent, mitigating the Sn²⁺ 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 N₂ glovebox. Additionally, this strategy enabled high-performance HTL-free PDs with a remarkable specific detectivity beyond 10¹⁴ Jones at 920 nm. This work provides a strategic pathway for developing efficient HTL-free Sn-Pb perovskite optoelectronic devices.