Improving the performance of low-temperature planar perovskite solar cells by adding functional fullerene end-capped polyethylene glycol derivatives

Functional fullerene derivatives play an important role in improving the performance of perovskite solar cells (PSCs) by promoting charge transfer and passivating trap states in perovskite film. In this work, the planar PSCs with the structure of FTO/TiO2/modified CH3NH3PbI3/Spiro-OMeTAD/Ag are fabricated by one-step method. Fullerene end-capped polyethylene glycol derivative (PCBPEG) is synthesized by a simple process and added into the perovskite precursor solution to improve microstructure and photoelectric properties of PSCs. At the optimum concentrations of PCBPEG additives and the annealing time of perovskite film, PSCs with PCBPEG additives yield the average efficiency of over 17.3%, being much higher than 15.28% of the reference PSC. Moreover, the unencapsulated PSCs with PCBPEG additives prepared at the optimal process demonstrate the enhanced stability. Compared to the reference perovskite film, the modified perovskite films demonstrate larger grain size, improved electric properties at nanoscale level and reduced electron trap state density, which will contribute to the favorable photovoltaic performance. The improved performance of the modified PSCs is primarily attributed to the promoted carrier transfer and suppressed charge recombination. These results provide a facile and feasible method to fabricate functional fullerene for high performance PSCs.