Nanopillars assisted multilayer antireflection coating for photovoltaics with multiple bandgaps

Abstract

A nanopillar assisted multilayer antireflection (AR) coating that combines the Ta2O5/SiO2 multilayer with SiO2 nanopillars was investigated to improve the light absorption of quadruple-bandgap photovoltaics. After clarifying that the performance of the traditional multilayer AR coating is restricted by the available refractive index of the top layer, periodic SiO2 rhombic nanopillars that work in the subwavelength regime were used to vary its effective index from 1 to 1.46. Then, the effective index and thickness of SiO2 nanopillars were optimized together with the Ta2O5/SiO2 stack using the global optimization algorithm to further reduce the reflection loss. When the SiO2 nanopillars have an effective index of 1.15 and a thickness of 108 nm, the best AR performance was achieved with a reflectance of 3.9% in the target spectral range of 300–1700 nm. Using laser interference lithography and ion assisted deposition technologies, the nanopillar assisted AR coating was realized with a reflectance of 4.5%. Compared to the traditional multilayer AR coating, this hybrid approach can not only achieve better AR performance but also reduce the disparities of the reflection loss among different bandgaps, which helps us to effectively improve the current matching and enhance the overall efficiency of quadruple-bandgap photovoltaics.

How the morning-afternoon cloudiness asymmetry affects the energy-maximizing azimuth direction of fixed-tilt monofacial solar panels

“…Until now we have dealt with fixed-tilt monofacial solar panels having a smooth, Fresnel-reflecting (R > 0) cover surface. Nowadays, solar panels with an anti-reflective (matte) cover surface are gradually spreading [22][23][24][25]. The reflectivity of such matte covers is very small: 0 < R ≪ 1.…”

Light‐trapping and spectral modulation to increase the conversion efficiency of triple‐junction GaAs solar cells using antireflective coating comprising a periodic array of cone‐shaped TiO 2 structures

“…Multilayer anti-reflective coatings with graded-index, refractive index, or high-low refractive index could conceivably be used to distribute light among sub-cells. [28][29][30][31][32] Nevertheless, light-trapping is generally more difficult in multiple-junction solar cells than in single-junction solar cells, 33,34 due to the need to preserve broadband absorption and deal with the issue of photo-current mismatch between sub-cells. In the current study, we developed a novel antireflective coating with surface nano-structures to enhance current matching and conversion efficiency in the top and middle cells of triplejunction (3 J) GaAs solar cells.…”

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