Fluorene-Modified Zinc-Porphyrin as Low-Cost Hole Transporting Material for Efficient Perovskite Solar Cells

The potential of porphyrin derivatives as hole-transporting materials (HTMs) for perovskite solar cells (PSCs) has been demonstrated. The structural engineering of porphyrin HTMs provides an important means for further improvement of the performance of PSCs. Herein, a zinc-porphyrin derivative (ZnP-FL) decorated with four fluorene-terminated triarylamines is presented. The lab synthesis cost of ZnP-FL is estimated to be around 32.2 $/g. It exhibits good charge-transport ability and thermal stability. A high power conversion efficiency (PCE) of 19.31% is achieved by using ZnP-FL HTM (Voc = 1.08 V; Jsc = 24.08 mA cm−2), which is distinctly higher than that of a control HTM without the fluorene groups (PCE = 17.75%; Voc = 0.97 V; Jsc = 24.04 mA cm−2). This performance enhancement is mainly attributed to the improved open-circuit voltage, which benefits from the stabilized HOMO level of ZnP-FL. In addition, the porphyrin HTM-based PSCs show superior air and thermal stability to the device with the standard HTM spiro-OMeTAD. These results demonstrate that the low-cost and easily-accessible porphyrin derivatives are promising HTMs for efficient and stable PSCs.