Highly Stable and Efficient N‐I‐P Structured Tin‐Rich Lead‐Tin Halide Perovskite Solar Cells with Blended Hole‐Transporting Materials

Abstract Mixed lead‐tinv halide (LTH) perovskite solar cells (LTH‐PSCs) can reduce the toxicity concerns of full lead‐based PSCs and potentially optimize the bandgap to maximize efficiency. However, commonly used hole‐transporting material (HTM) 2,2′,7,7′‐tetrakis(N,N‐di‐p‐methoxyphenyl‐amine)9,9′‐spirobifluorene (Spiro‐OMeTAD) with additional dopants Li‐bis(trifluoromethanesulfonyl) imide (Li‐TFSI) and 4‐tert‐butylpyridine (t‐BP) deteriorate oxidation Sn 2+ to Sn 4+ leading to trap formation. Here, the study introduces a novelty Sn‐friendly HTM for Sn‐rich LTH‐PSCs, combining Spiro‐OMeTAD with 4‐Isopropyl‐4′‐methyldiphenyliodonium tetrakis(pentafluorophenyl)borate (dpi‐TPFB) as a dopant and blended with poly(3‐hexylthiophene‐2,3‐diyl) (P3HT). This blended HTM avoids the harmful effects of Li‐TFSI and t‐BP dopants and leverages the beneficial hydrophobic properties of P3HT, which predominantly resides on the surface with a face‐on orientation. This arrangement not only enhances charge transport and extraction but also improves device stability by protecting the perovskite from environmental factors. Optimizing the P3HT concentration of blended HTM achieved a PCE of 17.27%, the highest reported for n‐i‐p structured Sn‐rich mixed LTH‐PSCs. This HTM also significantly improved device stability, maintaining over 90% of the initial PCE after 3000 h of storage and 80% under maximum power point tracking (MPPT) for 550 h in the air.