Characterization of Deep Junction Fabricated by Laser Doping Using Internal Quantum Efficiency

Internal quantum efficiency of cells after laser assisted processes has been studied in this work. A 1070 nm CW laser beam was used for doping a p-type substrate from a predeposited spin-on dopant source. External and internal quantum efficiencies were measured. The IQE of the cell suggests formation of deep junction after laser doping. To study this, PC1D simulation has been done for different junction depth and similar shape of IQE curve is obtained when junction depth is more than 2 μm. Laser assisted drive-in was then performed on finished solar cell. The laser beam scan speed was varied and its effect on IQE was measured. The IQE suggests a small variation of junction depth with scan speed however surface quality is expected to be different. From the comparison of PC1D simulation and experimental data, a junction depth of 9 μm is obtained for uniform doping profile of the emitter.