Microstructuring and doping of monocrystalline silicon with femtosecond and nanosecond laser pulses

Monocrystalline silicon (c-Si) surfaces were microstructured and hyperdoped in SF6 atmosphere using femtosecond(fs) Ti:sapphire and nanosecond(ns) Nd:yttrium-aluminum-garnet laser pulses, respectively, for photovoltaic applications. The obtained microstructures were studied with respect to surface morphology, crystallinity, concentration and distribution of sulfur impurities. The experimental results indicate that the ns-laser microstructured silicon has a lower sheet resistance, a lower defect density (i.e., higher crystallinity) and a higher concentration of sulfur impurities distribution over a larger surface area and depth (about 1 m). In addition, its absorbance can reach about 80% from the visible region to the near-infrared spectral region. With the better performance of ns-laser treated silicon, solar cells with an active area of 8 cm2 were manufactured on the samples. The series resistance, open-circuit voltage, short-circuit current density, and conversion efficiency of the best solar cell are 0.5 , 503 mV, 35 mA/cm2, and about 12%, respectively. And these can be further improved by manufacturing process optimization.