Optimized rapid thermal process for high efficiency silicon solar cells

Rapid thermal processing is opening new possibilities for a low-cost and en vironmentally safe silicon solar cell production, keeping the process time at high temperature in the order of 1 min, due to enhanced diffusion and ox idation mechanisms. Controlling the surface concentration of the junction i s one of the major parameters, in order to obtain suitable front surface re combination velocities. Simultaneous diffusion of phosphorus and aluminum i s used to realize emitter and back surface field in a single high-temperatu re step, with optimized gettering effect. Controlling the mentioned paramet ers on industrial 1 Omega cm Ct material lead in 17.5% efficient solar cell s on a surface of 25 cm(2). All results are discussed in terms of process t emperature, dopant source concentration and effective process time, below 1 min including high heating and cooling rates. (C) 2001 Elsevier Science B. V. All rights reserved.