Core Structure Engineering in Hole-Transport Materials to Achieve Highly Efficient Perovskite Solar Cells

In this work, the thiadiazolopyridine (PT) unit was introduced as the core structure, with N-3,N-3,N-6,N-6-tetrakis(4-methoxyphenyl)-9-phenyl-9H-carbazole-3,6-diamine as the peripheral group, to obtain a new compound, JY8, for use as a hole-transport material (HTM) in planar perovskite solar cells (PSCs). Compared with the previously reported JY5 with benzothiadiazole as the core structure, the PT unit with stronger electron-withdrawing ability enhanced the intermolecular dipole-dipole interaction. Moreover, the introduction of the PT unit made the central part in JY8 more planar than its analogue JY5, which is conducive to charge transport. Field-emission (FE)-SEM images suggested a smooth and condense morphology of the JY8 film, which could improve the contact between the perovskite layer and the metal electrode. Space-charge limitation of current results, steady-state, and time-resolved photoluminescence decay curves indicated that JY8 as HTM facilitated hole extraction and hole transport. Consequently, planar PSCs fabricated with JY8 as the HTM exhibited a decent efficiency of 19.14% with a high fill factor of 81%.