Softly Doped and Deep Emitters for P/Al Solar Cell Structure

32nd European Photovoltaic Solar Energy Conference and Exhibition; 742-747
Objective of this work is to get softly doped and deep emitters in single thermal step. Due to high temperature diffusion, dead layer (electrically inactive) is formed which produces recombination centers and increases saturation current density (Joe). For appropriate choice of selective emitter in order to decrease emitter saturation current density (Joe), it is necessary to have a passivated emitters, i.e. with silicon nitride. We have presented a process which combines with standard technology used for selective emitter formation in a single thermal step which leads to lowly doped and deep emitters. This process is feasible for industrial fabrication of P/Al solar cells. In this process the gettering is higher than conventional process. Surface concentration value ranging from 3.6x1019 cm-3 to 7.2x1019 cm- 3 and depth junction values from 0.52 to 0.71 μm for sheet resistance ~100 Ω/ has obtained. The estimated saturation current density (Joe) could be around 30-40 fA/cm2 with optimization but in present work Joe is under 80 fA/cm2.