A study on passivation improvement in n-passivated emitter rear totally diffused solar cell using rapid thermal annealing

An investigation on enhanced surface passivation in the existing industrial process line of large area n -type silicon (Si) Passivated Emitter Rear Totally diffused ( n - PERT) solar cell has been performed. The Rapid Thermal Process (RTP) optimization for 20 min is conducted in the temperature range of 500–900°C and device evaluation is carried out with respect to regularly processed n -PERT solar cell. The impact of pre-metallization annealing is studied with the support of cell parameters like shunt resistance, reverse saturation current density determined from current-voltage measurements. The enhanced surface passivation via hydrogenation from silicon nitride (SiN x ) layer during annealing is established with the help of external quantum efficiency, spectral response measurements and Fourier transform infrared spectroscopy analysis. The addition of optimized annealing resulted in improvement by 550% (from 38 to 247 µs), 7.73% (from 630.7 to 678.8 mV) and 84.77% (from 223.3 to 34 cm/s) in effective minority carrier lifetime, implied open circuit voltage and surface recombination velocity respectively. Finally, RTP technique for optimized process line has been successfully incorporated in industrial high-volume batch of 140898 CZ n-type Si wafers, which predicts conceptual validation of the study in mass scale production line with an increment in average efficiency of the device by 0.35%.