Pulsed laser techniques for solar cell processing

Abstract

Q-switched lasers can serve as energy sources to replace conventional high-temperature furnaces in p-n junction formation in solar cells. They have been used to anneal ion-implantation damage, to produce laser-assisted dopant diffusion, and to regrow doped amorphous layers deposited on single-crystal Si substrates. It has been demonstrated that all these methods are suitable candidates for the processing of high-efficiency Si solar cells. Because they provide ultrarapid heating and cooling of the near-surface region, these laser techniques can be used for p-n junction formation in thin-film polycrystalline material to prevent enhanced dopant diffusion along grain boundaries and for compound semiconductors, such as GaAs, to avoid the need for surface encapsulation during the annealing of ion implantation damage. Defects in the near-surface region such as the "dead layer" produced by conventional high-temperature diffusion can be completely removed by laser irradiation.