Efficient Perovskite Solar Cells by Employing Triphenylamine-Functionalized Azadipyrromethene Dyes as Dopant-Free Hole-Transporting Materials and Bidentate Surface Passivating Agents

In this study, a series of dopant-free, low-cost hole-transporting materials (HTMs) based on triphenylamine-functionalized azadipyrromethene dyes <b>1-3</b> (TPA-ADPs <b>1-3</b>) were designed and synthesized. The properties of these new HTMs were investigated by optical spectroscopy, cyclic voltammetry, thermogravimetric analysis, differential scanning calorimetric, atomic force microscopy, and X-ray diffraction, as well as theoretical calculations. The results indicated that the TPA-ADPs <b>1-3</b> presented well-matched energy levels with perovskite, higher hole mobility, as well as more effective defect passivation at the perovskite/HTM interface by the coordination interaction between the ADP moiety and the undercoordinated Pb²⁺. The n-i-p perovskite solar cells (PSCs) employing HTMs <b>1-3</b> as well as doped Spiro-OMeTAD were fabricated and characterized. The TPA-ADP <b>1</b>-based PSCs exhibited the best performance with a champion power conversion efficiency (PCE) of 22.13% and an fill factor of 0.81, which was superior to that of the devices based on the doped Spiro-OMeTAD. Long-term device performance studies indicated that the TPA-ADP <b>1</b>-based PSCs maintained 80% of the initial PCE after 1800 h of storage in the ambient condition of 40-60% RH, which was also higher than the stability of doped Spiro-OMeTAD-based devices under the same conditions.