Room-temperature larger-scale highly ordered nanorod imprints of ZnO film

Abstract

Room-temperature large-scale highly ordered nanorod-patterned ZnO films directly integrated on III-nitride light-emitting diodes (LEDs) are proposed and demonstrated via low-cost modified nanoimprinting, avoiding a high-temperature process. with a 600 nm pitch on top of a critical 200 nm thick Imprinting ZnO nanorods of 200 nm in diameter and 200 nm in height continuous ZnO wetting layer, the light output power of the resulting integrated ZnO-nanorod-film/semi-transparent metal/GaN/InGaN LED shows a two-fold enhancement (100% light extraction efficiency improvement) at the injection current of 150 mA, in comparison with the conventional LED without the imprint film. The increased optical output is well explained by the enhanced light scattering and outcoupling of the ZnOrod structures along with the wetting film, as verified by the numerical simulations. The wetting layer is found to be essential for better impedance matching. The current-voltage characteristics and electroluminescence measurements confirm that there is no noticeable change in the electrical or spectral properties of the final LEDs after ZnO-nanorod film integration. These results suggest that the low-cost high-quality large-scale ZnOnanorod imprints hold great promise for superior LED light extraction.

Light Extraction Efficiency Enhancement of Colloidal Quantum Dot Light‐Emitting Diodes Using Large‐Scale Nanopillar Arrays

“…It has been previously demonstrated that photonic crystal nanostructures can be used above the glass surface for enhancing the LEE of an OLED device where the trapped light within the QLED escapes into the air as a result of Bragg diffraction and scattering from the nanostructures on the glass surface . Among them, ZnO nanostructures are promising materials as light outcoupling medium because of their high index and excellent optical transparency as well as easy solution fabrication process . For our case, the light extraction enhancement in QLEDs is investigated by placing ordered ZnO nanopillar arrays onto the glass surface of ITO‐glass substrates, as shown in Figure a.…”

Light Trapping in Inverted Organic Photovoltaics With Nanoimprinted ZnO Photonic Crystals

“…Nanoimprinting of photonic crystal layer has been demonstrated on active layer of both regular and inverted OPV and has been proven to be compatible with large-scale fabrication, as well as with a range of materials [15], [17]. The photonic crystal structure used for this experiment was obtained by a method similar to that reported in the literature [23]. The initial step in the process was to prepare the polydimethylsiloxane (PDMS) mold, which was used to create the ZnO photonic crystal layer, as shown in Fig.…”

Zinc Oxide Nanophotonics

“…Due to the p-type doping problem, many researchers reported on the heterostructures with n-type ZnO grown on p-type materials of Si, GaN, and conducting oxides [27,54,140,141]. Among the possible heterostructures, the structure ZnO/GaN has attracted extensive interest [142][143][144] because device structures such as n-ZnO/pGaN can be readily realized because the lattice mismatch between ZnO and GaN is modest (1.9%) [145]. Another alternative p-type material is Si [146].…”