ZnO Nanostructures as Efficient Antireflection Layers in Solar Cells

Abstract

An efficient antireflection coating (ARC) can enhance solar cell performance through increased light coupling. Here, we investigate solution-grown ZnO nanostructures as ARCs for Si solar cells and compare them to conventional single layer ARCs. We find that nanoscale morphology, controlled through synthetic chemistry, has a great effect on the macroscopic ARC performance. Compared with a silicon nitride (SiN) single layer ARC, ZnO nanorod arrays display a broadband reflection suppression from 400 to 1200 nm. For a tapered nanorod array with average tip diameter of 10 nm, we achieve a weighted global reflectance of 6.6%, which is superior to an optimized SiN single layer ARC. Calculations using rigorous coupled wave analysis suggest that the tapered nanorod arrays behave like modified single layer ARCs, where the tapering leads to impedance matching between Si and air through a gradual reduction of the effective refractive index away from the surface, resulting in low reflection particularly at longer wavelengths and eliminating interference fringes through roughening of the air-ZnO interface. According to the calculations, we may further improve ARC performance by tailoring the thickness of the bottom fused ZnO layer and through better control of tip tapering.

One-dimensional ZnO nanostructures: Solution growth and functional properties

“…Antireflection coating layers play an important role in enhancing the device efficiency by increasing the light coupled with the active region of the solar cell [50,118,138,444]. ZnO is attractive for this purpose because of its good transparency, appropriate refractive index (n ≈ 2), and controllable textured growth [444].…”

Synthesis, luminescence properties and EPR investigation of hydrothermally derived uniform ZnO hexagonal rods

“…A large number of techniques like thermal decomposition, chemical vapor deposition, laser ablation, hydrothermal synthesis, sputtering, combustion, sol-gel process etc., [11][12][13][14][15][16] have been used for synthesis of many interesting morphological nanostructures of ZnO including nanoflowers, nanobelts, nanobridges, nanonails, nanoribbons, nanowires and nanorods. Compared with other preparation methods, hydrothermal synthesis is often used because it is carried out in a mild way at low temperature and allows control of size, morphology and crystallinity by tuning the experimental variables such as temperature, pressure, duration of process, concentration of chemical species and pH of solution.…”

Type-II Core/Shell Nanowire Heterostructures and Their Photovoltaic Applications

“…Compared with planar structure, nanowires can effectively enhance light absorption by suppressing light reflectance and increasing light coupling [16,17]. These advantages promote the development of nanowire-based solar cells.…”