Small Molecular Dibenzo[b,d]thiophene-Based Hole Transport Materials for Tin–Lead Perovskite Solar Cell

The most commonly used hole transport material (HTM) in tin–lead (Sn–Pb) perovskite solar cells (PSCs) is the aqueous poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS), and its inherent hygroscopic and acidic features greatly limit the power conversion efficiency (PCE) and stability of PSCs. Concerning this, by selecting dibenzo[b,d]thiophene 5,5-dioxide (DBTDO) as the core and engineering the donor units, 4-methoxy-N-(4-methoxyphenyl)-N-phenylaniline (TPA) and N1-(4-(bis(4-methoxyphenyl)amino)phenyl)-N4,N4-bis(4-methoxyphenyl)benzene-1,4-diamine (DTPA) as peripheral groups, two alternative HTMs are reported. Among them, the HTM TPA-DBTDO-DTPA can form a smoother film, which is conducive to the growth of dense perovskite film on it and shows the most suitable energy level. Meanwhile, the sulfonyl unit can passivate the buried defects of perovskite and improve the open-circuit voltage (VOC) of Sn–Pb mixed PSCs. Correspondingly, the TPA-DBTDO-DTPA-based PSC achieves a champion power conversion efficiency of 22.6% and maintains 75.9% of the initial PCE after aging 1000 h in a nitrogen (N2) environment, which fully outperforms the PEDOT:PSS-based control device.