Influence of back contact morphology on light trapping and plasmonic effects in microcrystalline silicon single junction and micromorph tandem solar cells

The quantum efficiency and short circuit current of microcrystalline silicon single junction and micromorph tandem solar cells significantly depend on the morphology of the metal back contact. Textured metal back reflectors improve light scattering and diffraction, but also increase optical losses in the back contact of the solar cells. The back contact morphology of microcrystalline silicon solar cell in superstate configuration is determined by the morphology of the textured front substrate and the texture introduced by the growth of the microcrystalline silicon film. A comparison of experimental data and optical simulations reveals that the optical losses associated with the metal back reflector are mainly determined by nano-features present at the metal reflector interface. The textures of the front substrate which propagate to the metal back reflector have only a minor influence on the optical losses. Different strategies will be presented on how to maximize the light trapping properties of the metal back reflector while minimizing the optical losses.