Textured substrate for high-efficiency n-i-p μc-Si:H solar cells

In this paper, we investigate the light scattering properties of our randomly textured back reflector (BR) for n-i-p thin-film microcrystalline silicon μc-Si:H) solar cells. The texture-etched ZnO:Al (AZO) covered with Ag is used as BR. The substrate temperature during the sputtering of AZO and the etching time are crucial for the morphology of the BR. An optimized substrate temperature can improve the morphology of etched AZO and optical performance of the BR, thereby increasing the photocurrent of solar cells. After Ag evaporation we obtain small features superimposed on the large features of the etched AZO. As a result the angle distribution becomes much wider. Large features of BR can preferentially scatter light into larger angles. The optimized BR has a wide surface angle distribution with an average angle of 27 ° and exhibiting a peak at 32 °. The optimized BR has a very broad reflective angular intensity distribution in air (AID_air) with peak at around 45 ° for incident light from 400 nm to 800 nm, and has a very high haze in reflection. With this optimized BR we obtained 7.68% efficiency for rf-PECVD deposited n-i-p μc-Si:H thin film solar cells. The J_sc is 25.2 mA/cm² with a very high quantum efficiency in the long wavelength region. And the VHF-PECVD deposited n-i-p μc-Si:H thin film solar cells prove that the optimized BR does not deteriorates the solar cells electrical performance and the obtained the best efficiency is 8.9%.