Enhanced photovoltaic performance of inverted pyramid-based nanostructured black-silicon solar cells passivated by an atomic-layer-deposited Al₂O₃layer

Abstract

Inverted pyramid-based nanostructured black-silicon (BS) solar cells with an Al2O3 passivation layer grown by atomic layer deposition (ALD) have been demonstrated. A multi-scale textured BS surface combining silicon nanowires (SiNWs) and inverted pyramids was obtained for the first time by lithography and metal catalyzed wet etching. The reflectance of the as-prepared BS surface was about 2% lower than that of the more commonly reported upright pyramid-based SiNW BS surface over the whole of the visible light spectrum, which led to a 1.7 mA cm(-2) increase in short circuit current density. Moreover, the as-prepared solar cells were further passivated by an ALD-Al2O3 layer. The effect of annealing temperature on the photovoltaic performance of the solar cells was investigated. It was found that the values of all solar cell parameters including short circuit current, open circuit voltage, and fill factor exhibit a further increase under an optimized annealing temperature. Minority carrier lifetime measurements indicate that the enhanced cell performance is due to the improved passivation quality of the Al2O3 layer after thermal annealing treatments. By combining these two refinements, the optimized SiNW BS solar cells achieved a maximum conversion efficiency enhancement of 7.6% compared to the cells with an upright pyramid-based SiNWs surface and conventional SiNx passivation.

One-step Maskless Fabrication and Optical Characterization of Silicon Surfaces with Antireflective Properties and a White Color Appearance

“…2e , only 15% of the incoming beam (per facet) falls in an area, where a third reflection could happen; the rest would be either reflected out of the inverted pyramid or absorbed by the pyramid (refracted). Similar hypothesis of triple reflections of inverted pyramids was also suggested by other groups 17 20 . Due to the restriction of our experimental setup, light scattered to angles lower than 17° to the sample normal could not be measured, which makes it difficult numerically to fit the two peaks or calculate their integral precisely.…”

“…2a,b ). The total reflectance of sample 55-10-10 (without anti-reflective coating) is lower than 20% at shorter wavelength, and as low as 12% at near IR, which is lower than many reported values of uncoated nano/micro inverted pyramids made by more complex methods 17 27 28 . The inverted pyramids of this sample (55-10-10) are almost arranged in a hexagonal array, and yet with a predominantly quadratic base having side lengths of around 600 nm and a pitch distance of around 700 nm, much smaller than those reported by Wang et al .…”

“…reported that it is possible to chemically and electrically passivate the black silicon to reduce the charge recombination by depositing an alumina layer 14 . Alternatively, it has been reported that inverted pyramids have lower surface areas than upright pyramids, yet still good light trapping properties 12 13 15 16 17 18 19 20 . These inverted pyramids are typically fabricated either by colloidal lithography 21 22 , or by combining interference lithography and wet silicon etching 13 16 17 19 .…”

Towards 30% Power Conversion Efficiency in Thin-Silicon Photonic-Crystal Solar Cells

“…Pyramid and inverted-pyramid [23,[41][42][43][44][45] surface structures have been useful in the design of classic solar cells that have achieved previous world-record efficiencies. These conventional designs utilize architectures with length-scales much larger than the wavelength of light to deflect sunlight in a classical ray-optics picture.…”

Realizing a facile and environmental-friendly fabrication of high-performance multi-crystalline silicon solar cells by employing ZnO nanostructures and an Al2O3 passivation layer

“…Based on these methods, the obtained mc -Si solar cells with highest conversion efficiency (CE) of 18%3, 19.1%10 and 20.3%12 have been reported. Unfortunately, the MCE technique is [001] oriented silicon preferred15161718, which is not very effective on the mc -Si surface. Because the formed Si NS is unable to distribute homogeneously on the surface owning to the random crystalline characteristic of the mc -Si, the light trapping ability will be degrade19.…”