Large area imprinted surface textures for omnidirectional conformal AR coatings on flexible amorphous silicon solar cells

Inverted pyramid surface textures are demonstrated on flexible amorphous Si solar cells based on a resin imprint process. The surface texture reduces the reflectivity of the cells over a broad spectrum. The texture leads to relative cell efficiency increases from 7% at 0° (surface-normal incident) to as high as 22% at 60°. Larger efficiency improvement at higher incident angles is a result of the broad spectrum omni-directional suppression in reflection. The current-voltage characteristics show that the open circuit voltage remains almost constant but the surface texture increases the short circuit current in the amorphous Si solar cell. This suggests that the efficiency improvement is primarily due to improved coupling of light into the cell. This omnidirectional surface texture is a promising method for anti-reflection in all kinds of cells-crystalline Si, amorphous Si, thin films, and organic solar cells.