Comparison of different emitter diffusion methods for MINP solar cells: Thermal diffusion and RTP

A solar cell technology with an extremely small thermal budget was developed for MINP cells. MINP solar cells with efficiencies of up to 15.3% have been achieved by rapid thermal processing (RTP). An emitter diffusion process was simulated and developed that yields a doping profile with a tunnelling oxide in a single furnace step. The P concentration profile was investigated by SIMS measurements and compared to the calculated profile. The SIMS results of the 850°C processing temperature differ from the calculated profile, but the 800°C values showed an excellent conformity. The surface passivation can be improved by an increase of the deposition temperature of the antireflection film. The maximum temperature was appointed with 400°C for MINP and 300°C for pn cells. In comparison with pn cells the temperature stability of MINP cells is significantly higher.