ANALYSIS OF OPTICAL ENHANCEMENT IN a-Si n-i-p SOLAR CELLS USING A DETACHABLE BACK REFLECTOR

We have used a novel device structure to study optical enhancement and back reflectors (BRs) in a-Si n-i-p solar cells by separating the effects of substrate texture, BR texture, and BR reflectivity. QE and diffuse and total reflection are compared for devices on smooth or textured substrates, with smooth or textured BRs. There is little improvement in J,, for substrate hare exceeding 5%. Substrate texture is much more effective at increasing red response than the BR texture. Smooth substrates with textured BRs have comparable diffuse reflection but much higher specular reflection than textured substrates with a smooth BR. Devices on textured substrates also have lower reflection losses in the blue regions, resulting in higher QE at all wavelengths. These results apply to both superstrate and substrate device configurations.