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Nanosecond laser treatment of a-Si thin films for enhanced light trapping and minority carrier lifetime in photovoltaic cells
Date Issued
01-12-2017
Author(s)
Vidhya, Y. Esther Blesso
Indian Institute of Technology, Madras
Abstract
For thin film solar cells, the efficient collection of light is a challenge, therefore an efficient light-trapping scheme, such as the textures, is required for achieving high light conversion efficien-cies. Laser texturing with a Q-switched, nanosecond pulsed Nd3+:YAG laser is used to create nano scale surface roughness in a-Si thin films that enhances light-trapping with simultaneous crystalliza-tion. Changes in surface morphology due to laser assisted texturing in air and water environments on 1-μm thick n-type amorphous silicon film deposited on p-type c-Si is observed using Optical profilometer and Atomic Force Microscopy. The light-trapping properties of textures are analyzed by optical reflectance measurements and compared with theoretical analysis. The extent of crystal-linity and the influence of structural characteristics on electronic properties are studied using I-V characterization and open circuit voltage decay method. Reduction in reflection is observed com-pared to planar surface indicating dependence of reflectance on surface textures which is in agree-ment with the theoretical analysis. After underwater annealing, efficiency of n-aSi/p-cSi solar cells is found to be increased (~ 2% to 3%) when compared to that in air and diffusion lengths of minori-ty carriers above 1-μm after laser.
Volume
12