Laser hyperdoping of silicon films for sub-bandgap photoconversion enhancement

Abstract

Problems such as poor open-circuit voltage (VOC) and low photogenerated charge-carrier collection usually exist in hyperdoped Si solar cells for sub-bandgap optoelectronic response. Here, (Si/Ti)n multilayer films were deposited on the front surface of monocrystalline Si solar cells with single p/n junction. The films were melted and crystallized using a 1064-nm nanosecond-pulsed laser to form Ti-hyperdoped Si (Si:Ti) films, serving as a n+ layer in the new solar cells. A reduction in light reflection, an increase in sub-bandgap infrared absorption, and a p/n/n+ structure for charge-carrier collection were used to increase both the sub-bandgap and above-bangap photocurrents of solar cells. Thus, the VOC and short-circuit current density (JSC) of a Si:Ti solar cell reached 613 mV and 41.1 mA⋅cm−2, respectively. Furthermore, its sub-bandgap infrared (IR) external quantum efficiency (EQE) and JIRSC increased by ∼ 100% and 79% than those of the monocrystalline Si solar cell substrate, respectively. Finally, the solar cell with a Si:Ti film thickness of 105 nm and an active area of 14.4 cm2 showed the highest photoconversion efficiency (18.6%), which increased by 29% than that of substrate (14.4%).