Passivation functionalized phenothiazine-based hole transport material for highly efficient perovskite solar cell with efficiency exceeding 22%

Hole transport material (HTM) is an indispensable part of highly efficient perovskite solar cells (PSC). Designing new HTMs with suitable energy levels and desired electronic properties is critical to realize efficient and stable PSCs. Herein, two phenothiazine (PTZ) core building block based HTMs, termed PTZ-Py and PTZ-Bz, are reported. Applied in PSCs, the research results manifest that the introduced pyridine group, on the one hand, can deeply impact the electronic properties (energy levels and charge carrier mobility) and film-forming property; on the other hand, can efficiently passivate the perovskite surface defects, in turn, enhance the power conversion efficiency (PCE) and device stability. Under the optimized fabrication conditions, the HTM PTZ-Py based PSC obtains the highest PCE of 19.9%, and maintains around 90% initial efficiency after 1000 h aging in ambient condition with RH 50-65%. By using PTZ-Py as interface layer together with Spiro-OMeTAD, an improved PCE of 22.1% was obtained.