Light soaking and thermal annealing effects on the micro-electrical properties of amorphous and nanocrystalline mixed-phase silicon solar cells

We report on the measurement of local current flow in hydrogenated amorphous and nanocrystalline mixed-phase n-i-p silicon solar cells in the initial, light-soaked, and annealed states using conductive atomic force microscopy (C-AFM). The C-AFM measurement shows that the nanometer-size grains aggregate and the local current densities in the nanocrystalline aggregation areas significantly decreased after light soaking and recovered to similar values as the initial state after annealing at a high temperature in vacuum. This result supports the twoparallel-connected-diode model for explaining the light-induced open-circuit voltage increase in the mixed-phase solar cells.