Optimization of laser doping process in crystalline silicon solar cells

Abstract

A large area selective emitter patterning scheme is developed and reported in the present study that features a single additional step compared to the standard process. Initially, trials are conducted to achieve a uniform base sheet resistance of 100±10 Ω/sq in p-type c-Si wafers using POCl3 diffusion on a large area 156 x 156 mm silicon wafers. Thereafter, employing a nanosecond, Q-switched, green laser and phosphosilicate glass layer (PSG) as a dopant source, areas below the front contact fingers are heavily doped while areas between them are kept lowly doped, thus realizing a selective emitter. This study refers to optimization of diffusion parameters to achieve uniform diffusion of base sheet resistance of 100±10 Ω/sq and optimization of laser parameters for achieving localized regions of high doping to attain selective emitter structure.