Erbium-doped nanocrystalline silicon thin films produced by RF sputtering: annealing effect on the ER emission

Abstract

In order to improve the transparent contact layer in amorphous silicon solar cells fabricated on low-temperature plastic substrates, Al and Ga doped ZnO films were deposited at room temperature on plastic and glass and their optical, electronic and structural properties were correlated and optimized. Aiming to explore light trapping effects, plastic substrates were laser textured and their haze and total transmittance and reflectance were compared with those of untextured substrates. Although the haze increased dramatically, from 1.7 to 78.9 %, the total transmittance of PET coated with ZnO:Ga decreased from 83.9 %, in the untextured substrate, to 58.5 % in the textured PET. The haze in reflected light of PET coated with Al increased from 4.3% to 66.2% after texturing but the total reflectance decreased from 70.1 % to 36.8 %. Therefore the untextured substrates were used in the solar cells. a-Si:H solar cells were deposited at a substrate temperature of 150ºC on plastic, in the superstrate p-i-n configuration, and on stainless steel, in the substrate n-i-p configuration. The efficiency is ~5% in both types of devices, limited by low Jsc and low fill factor.