Modeling charge transport in quantum dot light emitting devices with NiO and ZnO transport layers and Si quantum dots

Kumar, Brijesh; Campbell, Stephen A.; Ruden, P.P.

doi:10.1063/1.4816680

Cited by 23 publications

(35 citation statements)

References 28 publications

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“…NiO, owing to its natural p-type conductivity, a relatively large band gap (~3.7 eV) as well as a diversity of preparation methods, 30,31 was naturally deemed as a top choice for fabricating such a heterojunction device. Considering the fact that insulating Al 2 O 3 substrates used in our work may limit the electrode preparation for LED applications, an appropriate p-type conductive material acting as both holetransporting layer and transparent window was therefore needed to construct a ZnO-based p-n heterojunction.…”

Section: Resultsmentioning

confidence: 99%

Epitaxial growth of vertically aligned ZnO nanowires for bidirectional direct-current driven light-emitting diodes applications

et al. 2015

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We presented a comparative investigation on the morphological and structural properties of the produced ZnO nanowires (NWs) on c-Al 2 O 3 substrates under different preparation conditions. The effects of a lowtemperature nucleation layer, reaction pressure and light irradiation on the alignment, diameter and growth rate of ZnO NWs were evaluated in detail. It was found that the low-temperature nucleation layer acting as a supporting layer favored the formation of a transition layer featuring initially a rough surface and a high density of grain boundaries, guiding and facilitating the subsequent homoepitaxy of ZnO NWs grown on the top of developed (0001) facets of the new activation sites. The crystallinity and vertical alignment of epitaxial ZnO NWs were further optimized to achieve the best value, as the second growth stage was conducted with a higher reaction pressure and light irradiation, such that a relatively low full width at halfmaximum (701 arcsec) of the rocking curve could be obtained. The thermodynamical growth kinetics of the produced ZnO NWs via the two-step growth process was also investigated by monitoring the morphology evolution at different growth stages. Coaxial n-ZnO/MgO/p-NiO-core/shell NWs heterostructured light-emitting diodes (LEDs) were then fabricated and characterized, and a unique tunability of the electroluminescence (EL) spectra depending on the bias polarities was observed. We studied in detail the bicolor EL characteristic of the bidirectional direct-current driven LEDs and tentatively proposed carrier tunneling and hole generation models to explain such interesting features. 40 | CrystEngComm, 2015, 17, 40-49 This journal is

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Section: Resultsmentioning

confidence: 99%

Epitaxial growth of vertically aligned ZnO nanowires for bidirectional direct-current driven light-emitting diodes applications

et al. 2015

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“…QD-LEDs were first presented in the form of hybrid organic/inorganic light emitting devices by Colvin et al, and were later improved by Coe-Sullivan et al [11]. QD-LEDs can lead to improved color saturation in thin film displays [2].…”

Section: Introductionmentioning

confidence: 98%

“…QDs exhibit prominent properties such as good photostability, high luminescence efficiency and facile color tunability by the quantum confinement effect and low-cost solution process ability [2,3,5,8,[10][11][12][13][14][15][16]. Quantum dots may be categorized by their synthetic routes as either ‗colloidal' or ‗epitaxial' (also known as ‗self-assembled').…”

Section: Introductionmentioning

confidence: 99%

High-Performance Solution Processed Inorganic Quantum-Dot LEDs

Amini

Dolatyari

Rostami

et al. 2015

IEEE Trans. Nanotechnology

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In this research paper, fabrication of novel CdSe\ZnS QD-LEDs with solution processing method is presented and the impact of trap energy levels in the electron and hole transport levels on these QD-LEDs brightness is investigated. Two types of QD-LEDs are fabricated with ITO as the transparent anode electrode, NiO nanoparticles as the hole transport layer (HTL), CdSe\ZnS QDs as the luminescent layer, ZnO: Ga as the electron transport layer (ETL), and Al as the cathode electrode. The NiO nanoparticles are synthesized by solgel or alternatively electrochemical method. Formation of different trap levels is observed in the crystal structures of the NiO nanoparticles synthesized by each of these methods. Considering the electrochemically prepared NiO nanoparticles, it is found that the density of trap levels is higher in the crystal structure of the NiO nanoparticles synthesized by sol-gel method and the device fabricated by the later material shows higher performance. Calculation of the electronic structure of ZnO: Ga by DFT methods (GGA-PBE) indicates that doping of Ga in the structure of crystalline ZnO creates new energy levels in conduction band and intermediate bands at the band gap of ZnO host. It facilitates electron injection from Al cathode to the ZnO:Ga ETL layer and from this layer to the QD luminescent layer. The fabricated devices show turn-on lower voltages than 5V in which a peak brightness of 500cdm -2 and 340cd m -2 is measured for the LEDs fabricated with sol-gel and electrochemically synthesized NiO nanoparticles respectively.Index Terms-Light emitting diode, Quantum dot, NiO, ZnO: Ga, Photo luminescence 1536-125X (c)

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“…QD-LEDs are multilayer structures, consist of hole transport layer (HTL), electron transport layer (ETL) and QD layer as an emissive layer. In this type of LEDs, Indium tin oxide (ITO) (as an anode) and Al (as a cathode) are used as usual electrodes [3,16]. At first QD-LEDs presented in the form of hybrid organic/inorganic light emitting diodes by Colvin et al [16].…”

Section: Introductionmentioning

confidence: 99%