Formation of Polycrystalline Silicon Films for Solar Cells by Flash Lamp Annealing

概要

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Flash lamp annealing (FLA) is a promising technique to form polycrystalline silicon (poly-Si) films for solar cells, because of its ms-order proper annealing duration which enables to sufficiently heat μm-order-thick a-Si films without inducing thermal damage onto whole glass substrates. The flash-lamp-induced crystallization of amorphous Si (a-Si) takes place laterally triggered by the release of latent heat, generally referred to as explosive crystallization (EC). The rapid lateral crystallization results in the suppression of hydrogen desorption out of Si films and the preservation of original dopant profiles, which are of great advantages to the realization of high-efficiency solar cells. We can obtain poly-Si films both consisting only of μm-order-long large grains and containing 10-nm-sized fine grains, depending on the method of preparing precursor a-Si films. Based on the results of multi-pulse FLA experiment, this can be explained as the emergence of different EC modes.