Abstract
Conical frustums with quasihexagonal nanostructures are fabricated on an InGaP window layer of single junction GaAs solar cells using a polystyrene nanosphere lithography technique followed by anisotropic etching processes. The optical and photovoltaic characteristics of the conical frustum nanostructured solar cells are investigated. Reflectance of the conical frustum nanostructured solar cells is significantly reduced in a wide range of wavelengths compared to that of the planar sample. The measured reflectance reduction is attributed to the gradual change in the refractive index of the InGaP conical frustum window layer. An increase of 15.2% in the power conversion efficiency has been achieved in the fabricated cell with an optimized conical frustum nanostructure compared to that of the planar cell.
Highlights
Fresnel reflection of incident light comes from the large difference of refractive indexes at the interface between the two materials, especially for air and semiconductor materials
To investigate the influence of the height of the conical frustum on the performances of the GaAs solar cells, the top diameter of the conical frustum is kept at a constant value of 380 nm while the height of the conical frustum is varied from 60 nm (Figure 2(e)) to 140 nm (Figure 2(f))
There is a gradual change in the refractive index, resulting in the Fresnel reflection suppression, when wavelengths of incident light are larger than the spacing of the protuberances [18]
Summary
Fresnel reflection of incident light comes from the large difference of refractive indexes at the interface between the two materials, especially for air and semiconductor materials. Under strong illumination in space or concentration applications, ARC has several problems such as mechanical and thermal stability, adhesion, and thermal mismatch To overcome these issues, surface patterning with subwavelength structures is introduced as an alternative technique for reduction of incident light reflectance [5, 6]. The nanosphere lithography technique is introduced and has attracted lots of attentions as one of the promising cost-effective subwavelength structure fabrication methods for the solar cell applications In this technique, polystyrene and silica nanoparticles are usually utilized, and a shadow mask can be formed on the surface of the substrates with a hexagonal geometry without any annealing process [15, 16]. Conical frustums with the quasihexagonal nanostructures are fabricated on the InGaP window layer of the single junction GaAs solar cells using a polystyrene nanosphere lithography technique followed by anisotropic etching processes. The photocurrent response of the fabricated cells is investigated at room temperature using a quantum efficiency measurement system (PV Measurements: QEX7)
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