This work demonstrates antisolvent treatment of organo-metal halide perovskite film in hole-conductor-free perovskite-based solar cell, achieving impressive power conversion efficiency of 11.2% for hole-conductor-free cells with gold contact. We found that antisolvent (toluene) surface treatment affects the morphology of the perovskite layer, and importantly, it also affects the electronic properties of the perovskite. Conductive atomic force microscopy (cAFM) and surface photovoltage show that the perovskite film becomes more conductive after antisolvent treatment. Moreover, the antisolvent treatment suppresses the hysteresis commonly obtained for perovskite-based solar cells. When the perovskite alone is characterized, a I-V plot of a single perovskite grain measured by cAFM shows that hysteresis vanishes after toluene treatment. During toluene treatment, excess halide and methylammonium ions are removed from the perovskite surface, leading to a net positive charge on the Pb atoms, resulting in a more conductive perovskite surface, which is beneficial for the hole-conductor-free solar cell structure. The reliability of the surface treatment was proved by calculating the statistical parameters Z score and p value, which were 2.5 and 0.012, respectively. According to these values, it can be concluded with 95% confidence that the average efficiency of cells fabricated via surface treatment is greater than the average efficiency of cells without surface treatment. The statistical data support the impact of surface treatment on the photovoltaic performance of perovskite solar cells.
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© 2015 American Chemical Society.