Efficient Perovskite\nSolar Cells by Employing Triphenylamine-Functionalized\nAzadipyrromethene Dyes as Dopant-Free Hole-Transporting Materials\nand Bidentate Surface Passivating Agents

In this study, a series of dopant-free, low-cost hole-transporting\nmaterials (HTMs) based on triphenylamine-functionalized azadipyrromethene\ndyes <b>1–3</b> (TPA-ADPs <b>1–3</b>) were\ndesigned and synthesized. The properties of these new HTMs were investigated\nby optical spectroscopy, cyclic voltammetry, thermogravimetric analysis,\ndifferential scanning calorimetric, atomic force microscopy, and X-ray\ndiffraction, as well as theoretical calculations. The results indicated\nthat the TPA-ADPs <b>1–3</b> presented well-matched energy\nlevels with perovskite, higher hole mobility, as well as more effective\ndefect passivation at the perovskite/HTM interface by the coordination\ninteraction between the ADP moiety and the undercoordinated Pb<sup>2+</sup>. The n-i-p perovskite solar cells (PSCs) employing HTMs <b>1–3</b> as well as doped Spiro-OMeTAD were fabricated and\ncharacterized. The TPA-ADP <b>1</b>-based PSCs exhibited the\nbest performance with a champion power conversion efficiency (PCE)\nof 22.13% and an fill factor of 0.81, which was superior to that of\nthe devices based on the doped Spiro-OMeTAD. Long-term device performance\nstudies indicated that the TPA-ADP <b>1</b>-based PSCs maintained\n80% of the initial PCE after 1800 h of storage in the ambient condition\nof 40–60% RH, which was also higher than the stability of doped\nSpiro-OMeTAD-based devices under the same conditions.