Efficient Sn-Pb Perovskite Solar Cells Through Inhibiting Hole Accumulation

Sn-Pb perovskite solar cells (PSCs) own the highest theoretical efficiency due to their ideal bandgap. However, the efficiency of Sn-Pb PSCs remains 22-23% at present, which is much lower than Pb-based PSCs. One key reason lies in the Sn²⁺ oxidation issue. Here, this study demonstrates that apart from well-known chemical environmental oxidation, photo-generated holes and their accumulation are also a critical factor for Sn²⁺ oxidation in Sn-Pb PSCs. To address this issue, a non-planar hole transport layer (HTL) of P3CT/Me-4PACz is designed through solution micelle regulation. P3CT/Me-4PACz will form a 3D HTL film with a spike-like structure penetrating Sn-Pb perovskite bulk to accelerate hole extraction, thus inhibiting holes accumulation and Sn²⁺ oxidation. Resulted Sn-Pb PSCs exhibit the highest efficiency of over 24% with good operational stability, retaining 82% of initial efficiency after continuous MPP tracking for 1000 h at an elevated temperature of 55 °C.