Analysis of the impact of doping levels on performance of back contact - back junction solar cells

In this work, by exploiting two-dimensional (2-D) TCAD numerical simulations, we performed a study of the impact of the doping levels on the main figures of merit in the different regions of a crystalline silicon Back-Contact Back-Junction (BC-BJ) solar cell: the emitter, the Back Surface Field (BSF) and the Front Surface Field (FSF). The study is supported by a dark loss analysis which can highlight the contribution of several recombination mechanisms to the total diode saturation current. The efficiency curve as a function of doping level exhibits a bell-shape with a clearly identifiable optimum value for the three regions. The decrease in efficiency observed at lower doping values is explained in terms of higher contact recombination for BSF and emitter, and in terms of higher surface recombination for FSF. The efficiency decrease observed at higher doping values is ascribed to the higher surface recombination for FSF and Auger recombination for all cases.