Integrated ZnO nanotips on GaN light emitting diodes for enhanced emission efficiency

Zhong, Jiaming; Chen, H.; Saraf, Gaurav; Lu, Yicheng; Choi, C. S.; Song, Juan; Mackie, David M.; Shen, H.

doi:10.1063/1.2741052

Cited by 146 publications

(98 citation statements)

References 16 publications

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“…Based on these results, and combined with its transparency over the visible region as well as the ability to be grown into a variety of nanostructures, it is hoped that the ZnO NRA can be further tailored to improve the out-coupling of light from the emissive organic layers [50][51][52] .…”

Section: Resultsmentioning

confidence: 99%

ZnO Nanorod Arrays as Electron Injection Layers for Efficient Organic Light Emitting Diodes

Faria

Campbell

McLachlan

2015

Adv Funct Materials

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Nanostructured oxide arrays have received significant attention as charge injection and collection electrodes in numerous optoelectronic devices. Zinc oxide (ZnO) nanorods have received particular interest owing to the ease of fabrication using scalable, solution processes with a high degree of control of rod dimension and density. Here we implement vertical ZnO nanorods as electron injection layers in organic light emitting diodes (OLEDs) for display and lighting purposes. Implementing our nanorods into devices with an emissive polymer, poly(9,9-dioctyluorene-altbenzothiadiazole) (F8BT) and poly(9,9-di-n-octylfluorene-alt-N-(4-butylphenyl)dipheny-lamine) (TFB) as an electron blocking layer, brightness and efficiencies up to 8600 cd/m 2 and 1.66 cd/A were achieved. We highlight simple solution processing methodologies combined with post-deposition thermal processing to achieve complete wetting of the nanorod arrays with the emissive polymer. The introduction of TFB to minimize charge leakage and non-radiative exciton decay results in dramatic increases to device yields and provides an insight into the operating mechanism of these devices. We demonstrate the detected emission originates from within the polymer layers with no evidence of ZnO band-2 edge or defect emission. The work represents a significant development for the ongoing implementation of ZnO nanorod arrays into efficient light emitting devices.

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Section: Resultsmentioning

confidence: 99%

ZnO Nanorod Arrays as Electron Injection Layers for Efficient Organic Light Emitting Diodes

Faria

Campbell

McLachlan

2015

Adv Funct Materials

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“…Extensive efforts have been made to tackle this problem, such as roughening the emitting surface of the thin film [404,405], reshaping the geometry of the LED architecture [406,407], utilizing a resonant cavity [408], coupling with surface plasmons [409], fabricating photonic crystal structures [410,411], and using corrugated Bragg gratings [412]. Nanowire/ thin film heterostructures have been proposed to be a promising solution, considering the waveguiding properties of the nanowires that should enhance light extraction efficiency of the LED's [9,[413][414][415][416][417][418].…”

Section: Light Extractionmentioning

confidence: 99%

One-dimensional ZnO nanostructures: Solution growth and functional properties

2011

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One-dimensional (1D) ZnO nanostructures have been studied intensively and extensively over the last decade not only for their remarkable chemical and physical properties, but also for their current and future diverse technological applications. This article gives a comprehensive overview of the progress that has been made within the context of 1D ZnO nanostructures synthesized via wet chemical methods. We will cover the synthetic methodologies and corresponding growth mechanisms, different structures, doping and alloying, positioncontrolled growth on substrates, and finally, their functional properties as catalysts, hydrophobic surfaces, sensors, and in nanoelectronic, optical, optoelectronic, and energy harvesting devices.

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“…Such adverse effects undesirably lower the current injection efficiency and/or internal quantum efficiency of the integrated devices, although the light extraction efficiency is increased. On the other hand, ZnO nanorod arrays formed by the hydrothermal synthesis led to only 70% LEE improvement in comparison to the conventional LEDs [10]. This was unfortunately lower than that of the MOCVD-grown ZnO NRAs.…”

Section: Introductionmentioning

confidence: 82%

“…For surface roughening, a common technique is based on photo-electrochemical etching [7]. Recently, remarkable investigations on the LEE of GaN-based LEDs have also been reported employing ZnO nanostructures [8][9][10][11][12]. Using ZnO can effectively reduce the internal reflection due to the fact that the refractive index of ZnO is about 2, which is close to but smaller than that of GaN (n = 2.5).…”

Section: Introductionmentioning

confidence: 99%

“…In addition, ZnO exhibits over 90% optical transparency in the visible region. In these previous reports, ZnO nanorod arrays (NRAs) were formed either by using metal-organic chemical-vapor deposition (MOCVD) [8], hydrothermal synthesis [9,10], or nanoimprinting method [11,12]. Among them, ZnO NRAs grown by MOCVD system have exhibited a high level of 100% LEE enhancement from GaN LEDs at the current injection of 50 mA compared to the conventional GaN LEDs [8].…”

Section: Introductionmentioning

confidence: 99%

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

Kyaw¹,

Wang²,

Dev³

et al. 2013

Opt. Express

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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.

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Integrated ZnO nanotips on GaN light emitting diodes for enhanced emission efficiency

Cited by 146 publications

References 16 publications

ZnO Nanorod Arrays as Electron Injection Layers for Efficient Organic Light Emitting Diodes

ZnO Nanorod Arrays as Electron Injection Layers for Efficient Organic Light Emitting Diodes

One-dimensional ZnO nanostructures: Solution growth and functional properties

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

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