Abstract
GaN nanostructures with various effective refractive index profiles (Linear, Cubic, and Quintic functions) were numerically studied as broadband omnidirectional antireflection structures for concentrator photovoltaics by using three-dimensional finite difference time domain (3D-FDTD) method. Effective medium theory was used to design the surface structures corresponding to different refractive index profiles. Surface antireflection properties were calculated and analyzed for incident light with wavelength, polarization and angle dependences. The surface antireflection properties of GaN nanostructures based on six-sided pyramid with both uniform and non-uniform patterns were also investigated. Results indicate a significant dependence of the surface antireflection on the refractive index profiles of surface nanostructures as well as their pattern uniformity. The GaN nanostructures with linear refractive index profile show the best performance to be used as broadband omnidirectional antireflection structures.
Highlights
III-nitride (In, Al, Ga, -N) based semiconductor alloys with direct band gap and wide band gap tuning from deep ultraviolet (UV) to near infrared have a great potential to be applied for high efficiency concentrator photovoltaics (CPV) [1,2,3,4]
The results indicate significant reduction of surface reflection for these GaN nanostructures over a wide incident angle and broad wavelength range for both S and P polarizations
Studies of the surface reflection properties of GaN pyramid structures indicate its significant dependence on the nanostructure uniformity
Summary
III-nitride (In, Al, Ga, -N) based semiconductor alloys with direct band gap and wide band gap tuning from deep ultraviolet (UV) to near infrared have a great potential to be applied for high efficiency concentrator photovoltaics (CPV) [1,2,3,4]. Among the proposed antireflection technologies, surface texturing is an effective approach to reduce surface reflection which has been widely implemented in various solar cell devices. Surface texturing such as nanorods [12], nanopillars [13], nanocones [14], nanohemisphere [15] and nanopyramids [16] have been used. We have studied the surface antireflection properties of GaN based hemi-ellipsoid microdome structures, which could significantly reduce surface reflection over a broad wavelength range and a wide incidence angle [17]. The effect of the uniformity of GaN pyramids on surface reflection was investigated
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