Mesoporous TiO 2 layer suppresses ion accumulation in perovskite solar cells.

Ion accumulation in perovskite solar cells can be highly suppressed by a mesoporous TiO 2 layer. This is evidenced by the decrease of the ion-related electrostatic potential with increasing the thickness of the mesoporous layer, accounted for by the electron population in the shallow trap states of the TiO 2 nanocrystals.