Improved performance of thin-film solar cells using surface-morphology-controlled poly-Si films crystallized by flash lamp annealing

We improve the performance of thin-film solar cells using polycrystalline silicon (poly-Si) films formed by flash lamp annealing (FLA) of precursor amorphous Si (a-Si) films on glass substrates by modulating their surface structures. The surface morphology of the poly-Si films can be easily controlled by conventional wet chemical etching using mixed acid of HF and HNO3, accompanied by effective reduction in optical reflectance. Solar cells with the best performance are obtained when the poly-Si films have the smallest surface roughness. This enhancement of the performance can be understood as the improved coverage of the poly-Si surface with post-deposited doping layers as well as the more effective anti-reflection effect caused by the wet etching.