Enhancement of light extraction efficiency of InGaN quantum wells light emitting diodes using SiO2/polystyrene microlens arrays

Abstract

Improvement of light extraction efficiency of InGaN quantum wells light emitting diodes ͑LEDs͒ using SiO 2 /polystyrene microspheres was demonstrated experimentally. The utilization of SiO 2 /polystyrene microlens arrays on InGaN quantum wells LEDs, deposited via rapid convective deposition, allows the increase of the effective photon escape cone and reduction in the Fresnel reflection. Improvement of output power by 219% for InGaN quantum wells LEDs emitting at peak wavelength of 480 nm with SiO 2 /polystyrene microspheres microlens arrays was demonstrated.

Design and mechanism of cost-effective and highly efficient ultrathin (< 0.5 μm) GaAs solar cells employing nano/micro-hemisphere surface texturing

“…Moreover, the fabrication of 2-D closepacked microlens arrays with hemispherical shape employed for suppressing the total internal reflection and improving the light escape cone in light-emitting devices, has been developed by the rapid convective deposition method resulting in highly-dense arrays of hemispherical structures. [20][21][22] Similar fabrication methods are applicable for experimentally realizing the concept described in the current work.…”

“…Here it is worth noting that although the hemispherical nano/micro-pit array also provides an efficient light confinement design, 32 the fabrication of such structures is not that easy compared to the fabrication of the structure proposed in this study using the methods already developed. [20][21][22] Moreover, we just focus on the optimization of the array periodicity for the hemisphere surface texturing in this paper. Other structural parameters, i.e., various aspect ratios and shapes need to further optimized for realizing more efficient light absorption as recent works have also reported the fabrication of microlens-like structures with various aspect ratios 33 and shapes.…”

Light Management with Nanostructures for Optoelectronic Devices

“…The substantially increased output power can be attributed presumably to the increase in its effective photon escape cone. 128,129 In addition, the use of SiO 2 (n = 1.46)/ PS (n = 1.58) as the intermediate refractive index materials for the microlens arrays also leads to reduced Fresnel reflection in the GaN/PS/SiO 2 /air interface, as compared to that for the GaN/ air interface. Another similar strategy is the introduction of a scattering medium on the substrate.…”

Fabrication of Broadband Antireflective Sub-Micro Structures on 4H-SiC by Mesh Patterning Etching

“…Moreover, such coatings worked only ________________________ in a limited spectral range, and more efficient reflection reduction in a broad spectral range has been achieved by surface texturing. Surface sub-wavelength nanostructures has been proven to be an effective way to reduce the surface reflection on UV detectors and solar cells [7][8][9][10][11][12] or to enhance the light extraction on LEDs [5][6][7][8][9][10][11]. Surface nanostructures can normally be manufactured by wet or dry etching.…”

“…Due to the large refractive index discontinuity at the air-semiconductor material interface, SiC UV detectors and solar cell devices have a large surface reflection [5][6][7][8] and LEDs usually suffer from low light extraction efficiency because of the total internal reflection. A broadband antireflection or light extraction improvement can be achieved by applying a stack of antireflection coatings with appropriate designs [6][7][8]. However, this material system is limited by the availability of materials with suitable refractive indices and thermal expansion coefficients.…”