Lifetime analysis for comparing POCl₃ diffused emitter doping characteristics in p-type silicon solar cells using QSSPC

Analysis of the emitter property of solar cells is important because the emitter doping characteristics can affect the surface recombination velocity, contact resistance, emitter saturation current density, and cell efficiency. To analyze the emitter quality, we used the following methods: the four-point probe method, quasi-steady-state photoconductance (QSSPC), and secondary ion mass spectroscopy (SIMS). The four-point probe method is used to measure the doping dose in the emitter. Using QSSPC, we can characterize the emitter quality, including the lifetime of the emitter, and using SIMS, we can measure the concentration of dopants as a function of depth in the emitter. However, SIMS measurement is destructive and limited to the measurement of planar surface wafers. To solve this problem, we investigated the relationship between the minority carrier lifetime and the emitter doping profile using the QSSPC. The relationship between the lifetime and emitter doping profile showed that the lifetime of the emitter decreases as the emitter doping concentration increases. From this result, we performed a lifetime analysis for differently doped POCl3-diffused emitters. The results obtained using the theoretical model for the lifetime agreed with experimental SIMS measurement results, indicating that the model can be used as a quantitative model for comparing emitter doping characteristics.