Hysteresis passivation in planar perovskite solar cells utilizing facile chemical vapor deposition process and PCBM interlayer

Low-cost, high-effciency perovskite solar cells (PSCs) have the distinguished potential to be next commercialized photovoltaic devices. Chemical vapor deposition (CVD) process was regarded as an excellent choice as compared to solution deposition technique, however, the photovoltaic and stable performance of the former lags behind that of the latter. In this work, we propose a facile CVD pattern to fabricate PSCs, substrates covered by lead iodide (PbI2) sandwich-surrounded by the source methyl-ammonium iodide (CH3NH3I, MAI) powder. Heat and mass transfer, surface reactions are involved in the CVD deposition procedure. Numerical calculations present a uniform distribution of MAI vapor, contributing to homogeneous perovskite films with comparable surface morphologies, crystal structures and photovoltaic performances, despite of the notorious hysteresis. Herein, a PCBM ([6,6]-Phenyl C61 butyric acid methyl ester) interlayer is introduced before the PbI2 coating and the CVD process. Results show that even suffered from the torturous CVD procedure, the PCBM interlayer still works to passivating the bulk and interfacial recombination, reducing the hysteresis, improving the grain structure of perovskite films. Hence, the photovoltaic performance of PSCs enhances by 30%, and the filling factor difference between the forward and the reverse scan reduces to 6%.