Dibenzothiophene\nS, S‑Dioxide-Containing Dipolar\nMolecules As Efficient Hole-Transport Materials for <i>p‑i‑n</i> Perovskite Solar Cells

Organic–inorganic\nhybrid perovskite solar cells (OIH-PSCs)\nhave developed rapidly in the past decade, and the commercialization\nof OIH-PSCs demands low-cost hole-transport materials (HTMs) with\nhigh performance and stability. The present study synthesized two\norganic HTMs containing dibenzothiophene S-dioxide as the acceptor\nunit and triphenylamine as the donor (denoted by TPAF-SO2 and TPA-SO2).\nIn TPAF-SO<sub>2</sub>, the methoxy group and adjacent fluorine atom\nwere introduced to decrease the highest occupied molecular orbital\nenergy level. In TPA-SO<sub>2</sub>, the methyl sulfide group is the\nend group that can passivate the lead ion. TPAF-SO<sub>2</sub> and\nTPA-SO<sub>2</sub> exhibit hole-transport mobilities as high as 1.12\n× 10<sup>–3</sup> and 2.31 × 10<sup>–3</sup> cm<sup>2</sup> v<sup>–1</sup> s<sup>–1</sup>, respectively,\nand strongly passivate Pb vacancies. Compared with TPAF-SO<sub>2</sub>, TPA-SO<sub>2</sub> is more suitable for the growth of perovskite\ncrystals. The perovskite grown on the latter has a lower trap density\nand higher carrier mobility; thus, both the nonradiative recombination\nand the charge-transport loss are decreased. The OIH-PSC based on\nTPA-SO<sub>2</sub> as the HTM achieved a power conversion efficiency\n(PCE) as high as 22.08%, whereas the device based on TPAF-SO<sub>2</sub> achieved a PCE of only 18.42%. In addition, the unencapsulated device\nbased on TPA-SO<sub>2</sub> can maintain 85% of the initial PCE after\nbeing stored in N<sub>2</sub> for 1200 h, whereas the device based\non TPAF-SO<sub>2</sub> decayed rapidly to zero in 800 h under the\nsame conditions.