Diindolotriazatruxene-Based Hole-Transporting Materials for High-Efficiency Planar Perovskite Solar Cells

A novel set of hole-transporting materials (HTMs) based on π-extended diindolotriazatruxene (DIT) core structure with electron-rich methoxy-engineered functional groups were designed and synthesized via a facile two-step procedure. All compounds were afforded from inexpensive precursors without a complex purification process. Cyclic voltammograms indicate that the resulting HTMs exhibit suitable highest occupied molecular orbital (HOMO) energy levels, which facilitate efficient hole injection from the valence band of perovskites into the HOMO of DIT-based HTMs as confirmed by time-resolved photoluminescence. Notable power conversion efficiency of the planar perovskite solar cells with low-temperature device fabrication achieved 18.21% utilizing D2, which is competitive with the corresponding devices based on the common Spiro-OMeTAD-based HTMs. The results manifest that DIT-based compounds are promising HTMs for constructing high-efficiency planar perovskite solar cells with low-cost solution processing procedures.