Nanoscale potential distribution of grain boundary dependence on humidity of high performance Perovskite (CH3NH3PbI3) solar cell(Conference Presentation)

We report effects of controlled humidity in ambient condition on grain boundary potential and charge transport within the grains of Pervoskite films prepared by sequential deposited technique. Grain boundary exhibited variation of their electronic properties with change in humidity level from sample kept inside glove box to 75% RH. X-ray diffraction (XRD) indicates the formation of PbI2 phase with increasing humidity level. The degradation of Pervoskite solar cell is mainly associated with the increase of PbI2 phase with increase in humidity level and hydration of the grain boundaries with the formation of hydrated phases. Spatial mapping of surface potential in the Perovskite film exhibits higher positive potential at grain boundaries compared to the surface of the grains. Grain boundary potential barrier were found to increase from ~35 meV to 80 meV for perovskite film exposed to 75% RH level compared to perovskite film kept inside glove box. Nanoscale current sensing measurement (Cs-AFM) shows that charge transport in perovskit solar cell strongly depends in humidity level. Performances of the solar cell was maximum for 25% humidity with 14.01 %. Transient measurement shows decrease in charge carrier life time and charge transport time with increase in humidity level. Our results show strong correlation between humidity level, electronic grain boundary properties and device performance.