Sulfur-hyperdoped silicon nanocrystalline layer prepared on polycrystalline silicon solar cell substrate by thin film deposition and nanosecond-pulsed laser irradiation

摘要

Silicon (Si)-based solar cells are the main products in current photovoltaics market; therefore, any development in their conversion efficiency and cost effectiveness provides an extremely important contribution to the photovoltaic industry. Use of hyperdoping process for the achievement of Si sub-bandgap light absorption to improve conversion efficiency has attracted significant attention of researchers. However, several problems are encountered during this process such as the poor crystallinity, severe carrier recombination, and high series resistance loss. In this study, a sulfur (S)-hyperdoped Si nanocrystalline layer is prepared on a commercial polycrystalline Si solar cell substrate to efficiently utilize near-infrared (NIR) and visible lights, respectively. An inexpensive, rectangle shaped nanosecond-pulsed laser beam is used to rapidly irradiate Si-S-Si multilayered films to produce this hyperdoped layer via melting, vaporization, resolidification, and crystallization processes. The hyperdoped samples which have S impurity concentration in the range of 0.15 +/- 0.07-0.78 +/- 0.03 at.%, exhibit high NIR light absorptance (75-90%), high bulk carrier concentration ( = 10(19) electrons.cm(-3)) and mobility ( similar to 10(2) cm(2) V-1 s(-1)), and low sheet resistance ( 100 Omega.square(-1)) and resistivity ( similar to 10(-3) Omega cm). The results confirm that this method not only improves the laser processing efficiency and saves costs, but also realizes a stable liquid S-hyperdoping process to prepare a nanocrystalline layer with strong IR properties.