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

Sn-friendly hole transport material (HTM) for the n-i-p tin-reach, lead-tin halide perovskite solar cells (LTH-PSCs) is developed by mixing Spiro-OMeTAD with 4-Isopropyl-4'-methyldiphenyliodonium tetrakis(pentafluorophenyl)borate (dpi-TPFB) as a dopant and blended with P3HT. Within this blended HTM, hydrophobic P3HT predominantly resides on the surface of the HTM film with face-on orientation, resulting in a record-breaking efficiency n-i-p LTH-PSCs of 17.27% with great stability.

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 Sn²⁺ to Sn⁴⁺ 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.