Femtosecond laser induced nanocone structure and simultaneous crystallization of 1.6 mu m amorphous silicon thin film for photovoltaic application

In this paper, we have demonstrated the crystallization and simultaneous formation of the nanocone structure on the 1.6 mu m thick amorphous silicon (a-Si) film using a one-step femtosecond laser annealing approach. The a-Si layer is crystallized after the annealing process, as confirmed from their Raman spectra. Meanwhile, the conical structures with diameters ranging from 160 nm to 1.4 mu m are formed upon laser beam irradiation at different fluences, as deduced from scanning electron microscope and atomic force microscope characterization. The highest absorption is achieved when the sample is irradiated with a laser fluence of 588 mJ cm(-2). The developed process has potential applications in the fabrication of high efficiency and low cost Si thin-film solar cells. Moreover, the physics and mechanism involved in the laser annealing process are also discussed.