Ultraviolet Organic Light-emitting Diodes Research Articles

High-Performance Ultraviolet Organic Light-Emitting Diodes Enabled by Double Boron-Oxygen-Embedded Benzo[m]tetraphene Emitters.

Ultraviolet organic light-emitting diodes (UV OLEDs) have attracted increasing attention because of their promising applications in healthcare, industry, and agriculture; however, their development has been hindered by the shortage of robust UV emitters. Herein, we embedded double boron-oxygen units into nonlinear polycyclic aromatic hydrocarbons (BO-PAHs) to regulate their molecular configurations and excited-state properties, enabling novel bent BO-biphenyl (BO-bPh) and helical BO-naphthyl (BO-Nap) emitters with hybridized local and charge-transfer (HLCT) characteristics. They could be facilely synthesized in gram-scale amounts via a highly efficient two-step route. BO-bPh and BO-Nap showed strong UV and violet-blue photoluminescence in toluene with full width at half-maximum values of 25 and 37 nm, along with quantum efficiencies of 98 and 99%, respectively. A BO-bPh-based OLED showed high color purity UV electroluminescence peaking at 394 nm with Commission Internationale de l'Eclairage (CIE) coordinates of (0.166, 0.021). Moreover, the device demonstrated a record-high maximum external quantum efficiency (EQE) of 11.3%, achieved by successful hot exciton utilization. This work demonstrates the promising potential of double BO-PAHs as robust emitters for future UV OLEDs.

Electroluminescence efficiency and stability of near ultraviolet organic light-emitting diodes based on BCPO luminous materials

To date, in the traditional method of obtaining near-ultraviolet (NUV) light, mercury atoms, which can create a highly toxic heavy metal contaminant, have been used. Therefore, it is an important issue to obtain NUV light by using new environmentally friendly devices. In the last decade, the fabrication of near ultraviolet organic light-emitting diodes (NUV-OLEDs) has become a research hotspot in the field of organic electronics. However, when the electroluminescence wavelength is extended to shorter than 400 nm, higher requirements are put forward for the materials used for each functional layer in these devices. In this work, a wide bandgap small molecule material of BCPO is used as the luminescent layer. The electron-transporting and hole-transporting materials are determined based on the overlaps between absorption spectra of these materials and emission spectrum of BCPO. And NUV-OLEDs with electroluminescent peak wavelength at 384 nm are prepared. By using the optimal device structure, the maximum external quantum efficiency of the device reaches 2.98%, and the maximum radiance of the device reaches 38.2 mW/cm<sup>2</sup>. In the electroluminescence spectrum, NUV light with wavelengths below 400 nm accounts for 57% of the light emission. In addition, the device demonstrates good stability when biased at two different constant voltage modes. The multiple key factors which affect the stability of the device are analyzed in detail. Firstly, it is found that the high glass transition temperature (<i>T</i><sub>g</sub>) of hole-transporting material is very important for the long-time stability of this device. The poor device stability is closely related to the low <i>T</i><sub>g</sub> temperature of hole-transporting material. Secondly, due to the widespread use of PEDOT:PSS as hole injection material in OLEDs, the electron leakage from the hole-transpor layer into the PEDOT:PSS layer may cause significant damage to the conducting polymer. When bombarded with low energy electrons, bond breakage occurs on the surface of PEDOT:PSS, followed by the release of oxygen and sulfur, resulting in changes in conductivity and oxidation reactions with molecules of hole transport material. Thirdly, the photoelectrical stability of organic molecules is the most fundamental reason that restricts the device lifetime. The aging process of material or device is directly relevant to the bond dissociation energy (BDE) of organic molecule. Generally, the BDE value of organic molecule is not high enough. As a result, molecules are prone to chemical bond breakage during electrochemical or photochemical aging. In summary, highly stable NUV-OLEDs should be fabricated by using hole-transporting materials with high <i>T</i><sub>g</sub> temperature, sufficient electron-blocking capacity, and large BDE value.

High-Efficiency Ultraviolet Electroluminescence from Multi-Resonance Phosphine Oxide Polycyclic Aromatics.

Efficient ultraviolet (UV) electroluminescent materials remain a great challenge, since short peak wavelength <400 nm and narrow full width at half maximum (FWHM) <50 nm are simultaneously required. In this sense, multi-resonance (MR) thermally activated delayed fluorescence (TADF) emitters featuring narrow-band emissions hold the promise for UV applications. Herein, a novel MR-TADF skeleton featuring carbazole-phosphine oxide (P=O) fused aromatics is developed to construct the first two UV MR emitters named CzP2PO and tBCzP2PO. In addition to synergistic resonance effects of P=O and N atom, sp3 -hybrid P atom renders the curved polycyclic planes of CzP2PO and tBCzP2PO, giving rise to their narrowband UV emissions with peak wavelengths <390 nm and FWHM<35 nm. Besides configuration quasi-planarization for radiation enhancement and quenching suppression, P=O moiety further enhances singlet-triplet coupling to facilitate reverse intersystem crossing, resulting in the state-of-the-art photoluminescence quantum yield of 62 % in tBCzP2PO doped films. As consequence, tBCzP2PO endowed its UV organic light-emitting diodes with the peak at 382 nm and FWHM of 32 nm, and especially the record-high external quantum efficiency (EQE) of 15.1 % among all kinds of UV devices. Our results demonstrate great potential of P=O based MR emitters in practical applications including optoelectronics, biology and medicine science.

Donor–acceptor–donor molecules for high performance near ultraviolet organic light-emitting diodesviahybridized local and charge-transfer processes

Two bipolar molecules were designed with outstanding thermal stabilities. The molecules possess hybridized local and charge-transfer characteristics and exhibit high performance near ultraviolet electroluminescence with excellent color purity.

Tailoring hole injection of graphene oxide doped PEDOT:PSS for assembling efficient near ultraviolet organic light-emitting diodes

Tailoring hole injection plays a key role in near ultraviolet organic light-emitting diodes (NUV OLEDs) due to the wide band-gap and thus deep highest occupied molecular orbital level of emissive molecules. Solution-processed composite of graphene oxide doped poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS+GO) is facilely synthesized and served as hole injection layer of NUV OLEDs. The atomic force microscopy, ultraviolet photoelectron spectroscopy, impedance spectroscopy, Raman shift and infrared transmittance measurements confirm that PEDOT:PSS+GO shows superior film morphology and exceptional electronic properties such as enhanced surface work function, promoted hole injection capacity and improved device durability. With 9-(4′-(4,5-diphenyl-4 H-1,2,4-triazol-3-yl)-[1,1′-biphenyl]− 4-yl)− 9 H-carbazole as emissive molecule, the NUV OLED behaves superior short wavelength electroluminescence with emissive peak of 401 nm, maximum external quantum efficiency of 4.3 % and radiance of 14.3 mW/cm2, owing to the effective hole injection tailoring of PEDOT:PSS+GO and thus finely optimized carrier balance in the emissive layer. Our results pave an alternative approach for broadening GO applications and advancing short wavelength organic electroluminescence.

Investigation on carrier injection tailoring and electroluminescence of WSe2 quantum dots in light-emitting diodes

WSe2 quantum dots (QDs) with exceptional properties are facilely synthesized with liquid phase exfoliation and hydrothermal reaction, and characterized with scanning electron microscope, atomic force microscope, transmission electron microscope and X-ray photoelectron spectroscopy. The WSe2 QDs show good film morphology and effective carrier injection tailoring. Using 2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole as emitter, the near ultraviolet organic light-emitting diodes (NUV OLEDs) show maximum radiance of 1.25 mW/cm2 and external quantum efficiency (EQE) of 0.48% in inverted device with WSe2 QDs tailoring electron injection. The corresponding normal UV OLEDs show maximum radiance of 1.82 mW/cm2 and EQE of 1.39% with WSe2 QDs tailoring hole injection. Impedance spectroscopy analysis clarifies carrier injection tunability of WSe2 QDs. LEDs using WSe2 QDs as emitter are pioneeringly fabricated, showing maximum luminance of 426 cd/m2, EQE of 0.39%, luminous efficiency of 0.3 cd/A, power efficiency of 0.13 lm/W, and voltage dependent electroluminescent spectra. Ours results pave an alternative approach for interface modification, developing novel WSe2 QDs emitters, and boosting WSe2 QDs applications.

High-performance non-doped near ultraviolet OLEDs with the EQE ∼ 6 % and CIEy ∼ 0.03 from high-lying reverse intersystem crossing

Developing high-performance organic fluorophors with short-wavelength emission is both significant and challenging subject in the application of organic light-emitting diodes (OLEDs). In this work, we proposes a “coupling hardness with distortion” design concept to construct an efficient near ultraviolet (NUV) fluorophor mP2MPC with 1,4-dimethyl-2,5-diphenylbenzene as a rotatable bridge via the meta-positons linking rigid and bulky phenanthroimidazole and carbazole groups. As a result, the non-doped OLED with it as emitter not only exhibits an emission peak at 395 nm with the Commission Internationale de l’éclairage coordinates of (0.163, 0.028), but also realizes a high forward-viewing external quantum efficiency of 6.09 % due to the high-lying reverse intersystem crossing. The value still keeps as high as 5.56 % at 1000 cd m−2, showing a small efficiency roll-off. This is one of the highest efficiencies among the non-doped devices with the electroluminescence peak below 400 nm. Moreover, the green and red phosphorescent OLEDs with mP2MPC as host can also show excellent electroluminescence performance with the forward-viewing external quantum efficiencies over 21.5 %, illustrating that mP2MPC should be a prospective material for OLEDs.

High Steric‐Hindrance Windmill‐Type Molecules for Efficient Ultraviolet to Pure‐Blue Organic Light‐Emitting Diodes via Hybridized Local and Charge‐Transfer Excited‐State

AbstractHybridized local and charge‐transfer (HLCT) excited‐state compounds that enable full exciton utilization through a reverse intersystem conversion (RISC) from a high‐lying triplet to a singlet state have attracted attention. Developing high‐performance ultraviolet (UV) and blue organic light‐emitting diodes (OLEDs) is challenging due to difficulties acquiring HLCT molecules with a large energy bandgap and a high photoluminescence. Herein, a new strategy for excellent‐performance UV to blue emitters based on high steric‐hindrance windmill‐type structure is proposed. These emitters exhibit good thermal, morphological, and electrochemical stabilities, as well as HLCT excited‐state characteristics. Results suggest that OLED using CTPPI efficiently emits UV light (396 nm, CIEx,y = 0.16, 0.04) with a maximum external quantum efficiency (EQE) of 7.9% and currently ranks third in UV OLEDs. The lights of these devices are well modulated from UV/deep‐blue to pure‐blue with EQEs greater than 5% by regulating the locally excited (LE) and charge‐transfer (CT) components. Experimental and theoretical investigations indicate that harvesting triplet excitons afford high electroluminescence efficiencies via HLCT excited states in the devices. This study provides an efficient strategy to achieve high‐performance UV and blue OLEDs and offers great flexibility for material design.

High Efficiency and Low Roll-Off Non-Doped Near Ultraviolet Organic Light-Emitting Diodes with the Eqe Exceeding 6% and Ciey Smaller than 0.03

High Efficiency and Low Roll-Off Non-Doped Near Ultraviolet Organic Light-Emitting Diodes with the Eqe Exceeding 6% and Ciey Smaller than 0.03

The impact of ZnO nanotube on the performance of hybrid inorganic/organic light-emitting diode as a single-mode ring-core UV waveguide

After a systematic survey in hybrid inorganic/organic light-emitting heterostructure devices based on ZnO in the last decay, in this novel work, the impact of the single-mode ring-core waveguide based on ZnO nanotube (NT)/MEH-PPV for ultraviolet organic light-emitting diode (UV-OLED) application has been carefully scrutinized for the first time. The proposed structure has been fabricated, simulated and compared with conventional ZnO nanorod (NR)/MEH-PPV structure. To synthesize ZnO NTs, the as-grown chemical bath deposited ZnO NRs have been etched in KCL solution in various molar (M) concentration, etching time and etching temperature. The optimized etching condition is obtained in 1 M concentration of KCL solution, 4 h etching time and 90 °C temperature. The structural properties (such as strain, stress and texture coefficient), electrical properties (such as band gap energy) and optical properties (such as Urbach energy, absorbance and photoluminescence spectra) of ZnO NTs have been investigated, systematically. In continue, hybrid UV-OLEDs have been fabricated based on ZnO NRs and ZnO NTs. According to the results, ZnO NT-based OLED depicts superior electrical and optical results including lower turn-on voltage (11.2 V < 15 V) and higher UV peak in electroluminescence spectra with respect to ZnO NR-based device. To acquire more enlightenment about UV emission mechanism, the proposed devices have been simulated through Silvaco TCAD and Lumerical FDTD software. The results from simulations illustrate great agreement with experimental results. Higher radiative recombination rate, higher Purcell factor and single-mode waveguiding effect of ring-core ZnO NT lead to major superiority of the ZnO NT-based UV-OLED fabricated and simulated in this work.

Deep-blue organic light-emitting diodes based on multi-tert-butyl modified naphthylene

Six tert-butyls modified naphthyl derivative (2,6-di-tert-butyl-1,5-bis-(3,5-di-tert-butyl-phenyl)-naphthalene (N(dtb)4) was synthesized and tested for host and guest materials in organic light-emitting diodes (OLEDs). Blue OLED using N(dtb)4 as a host and an emitter DSA-PH as a guest reaches an efficiency of 11.52 cd·A−1 (maximum external quantum efficiency 7.8 % and maximum power efficiency 10.33 lm·W−1). In addition, for the OLED with N(dtb)4 being a guest, we find that the concentrations of N(dtb)4 will also affect the performance of the OLED, among which ADN: 5 wt.% N(dtb)4 has higher efficiency, and the maximum current efficiency, external quantum efficiency (EQE) and power efficiency of the device reach 3.75 cd·A−1, 3.93 % and 3.36 lm·W−1, respectively. We also investigated the pure N(dtb)4 -based ultraviolet OLED (UV-OLED), and achieved the maximum EQE of the device is 1.12 %. These results indicate that N(dtb)4, a novel synthesized fluorescent organic material, has great potential applications in OLEDs and accordingly advancing lightings and displays.

All solution-processed composite (ZnO+PEG)/Cs2CO3 with robust electron injection tailoring and its application to efficient inverted near ultraviolet organic light-emitting diodes

Electron injection/extraction is always highly emphasized in tailoring optoelectronic properties of organic electronic devices. Solution-processed ZnO, ZnO doped with poly(ethylene glycol) (ZnO+PEG) and composite (ZnO+PEG)/Cs2CO3 have been synthesized and characterized with X-ray diffraction, scanning electron microscope, energy dispersive X-ray spectroscopy, atomic force microscopy, X-ray/ultraviolet photoelectron spectroscopy. It is demonstrated that ZnO, ZnO+PEG and (ZnO+PEG)/Cs2CO3 exhibit superior film morphology and robust electron injection tailoring. With (ZnO+PEG)/Cs2CO3 as electron injection layer and 9-(4′-(4,5-diphenyl-4H-1,2,4-triazol-3-yl)-[1,1′-biphenyl]-4-yl)-9H-carbazole as fluorescent molecule, efficient inverted near ultraviolet organic light-emitting diode is assembled and gives satisfactory radiance of 10.6 mW cm−2 and external quantum efficiency of 1.9% with short-wavelength peaking at 409 nm and full width at half maximum of 52 nm, which are superior to the corresponding counterparts. The electron injection capacity of ZnO, ZnO+PEG and (ZnO+PEG)/Cs2CO3 are further confirmed by current-voltage characteristics, impedance spectroscopy transition curves and surface work function measurements. Such a solution-processed composite (ZnO+PEG)/Cs2CO3 also pave an alternative approach for constructing other multilayer electronic devices.

Solution-processed WS2 and its doping in PEDOT:PSS for tailoring hole injection in near ultraviolet organic light-emitting diodes

Solution-processed ethanol tungsten disulfide and its doping in poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) ( P E D O T : P S S + W S 2 ) for tailoring hole injection in near ultraviolet organic light-emitting diodes (NUV OLEDs) are investigated in detail. Raman spectrum, scanning electron microscopy, atomic force microscopy, x-ray/ultraviolet photoelectron spectroscopy, and impedance spectroscopy measurements show that W S 2 and its composites have superior film morphology and exceptional electronic properties. Using 2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole as the emitter and P E D O T : P S S + W S 2 as the hole injection layer, the NUV OLED produces short-wavelength emission peaking at 404 nm and full-width at half-maximum of 53 nm. The device also gives maximum radiance of 4.7 m W / c m 2 and external quantum efficiency of 2.1%, which are superior to counterparts using W S 2 , UV-ozone-treated W S 2 , and PEDOT:PSS. The hole injection ability is enhanced by using W S 2 , UV-ozone-treated W S 2 , PEDOT:PSS, and P E D O T : P S S + W S 2 in this order. The robust hole injection contributes to carrier balance and accounts for high device performance of the fabricated NUV OLEDs. Our results pave an alternative approach for advancing OLEDs and accelerating W S 2 applications.

Facilely solution-processed ZnO + Cs2CO3 for robust electron injection in ultraviolet organic light-emitting diode with inverted architecture

Electron injection governs electro-optic performance of organic light-emitting diodes (OLEDs) with intractable inverted architecture. Solution process with low cost and scalable manufacturing drives a lab-to-fab journey of electron injection layer (EIL) in OLEDs. Herein, a facilely solution-processed composite EIL of ZnO + Cs2CO3 with robust electron injection has been explored for constructing ultraviolet OLED with inverted architecture. Using 3-(4-biphenyl)-4-phenyl-5-tert-butylphenyl-1,2,4-triazole as emitter, attractive short-wavelength emission of 380 nm and full-width at half-maximum of 37 nm are demonstrated in the inverted ultraviolet OLED. It achieves maximum radiance of 2.42 mW/cm2 and external quantum efficiency of 0.85% with improved operation durability, which are superior or comparable to the corresponding references using single EILs of Cs2CO3, ZnO and LiF, or double-stacked EIL of ZnO/Cs2CO3. X-ray photoelectron spectroscopy analysis clarifies that the Cs2CO3, ZnO and ZnO + Cs2CO3 exhibit exceptional electronic properties. The current-voltage characteristics and impedance spectroscopy analysis of electron-only cells confirm that ZnO + Cs2CO3 behaves robust electron injection and accounts for excellent device performance. Our results pave an alternative approach for advancing ultraviolet OLED with inverted architecture and facile solution process.

Efficient near ultraviolet organic light-emitting diode based on PVK material doped with BCPO molecules

Near ultraviolet organic light-emitting diodes (NUV-OLEDs) have a wide range of applications. However, when large band-gap polymer of PVK was used as the emitting material, its poor electron transportation capability resulted in a large amount of charge accumulation on both sides of light-emitting layer/electron-transporting layer interface of the device, hence generating intense electroplex emission and seriously reducing the efficiency of NUV light-emitting. In order to solve this issue, BCPO molecules were doped in PVK with certain concentrations, forming PVK:BCPO mixing light-emitting layers. As compared with pure PVK, electron transportation capability was apparently increased in PVK:BCPO mixing layers. On one hand, charge accumulation at the interface was substantially weakened, and the electroplex emission was inhibited. On the other hand, transportations of electron and hole carriers became more balanced in light-emitting layer. Both of these improvements effectively promoted device performance. At appropriate BCPO doping concentration, the external quantum efficiency of PVK:BCPO-based NUV-OLEDs reached the maximum value of ∼2.6 %. Further experimental progress would bring it closer to the practical application in future.

Tailoring hole injection of sol-gel processed WOx and its doping in PEDOT:PSS for efficient ultraviolet organic light-emitting diodes.

Hole injection governs the efficiency of ultraviolet organic light-emitting diodes (UV OLEDs) due to the deep highest occupied molecular orbital level of the emissive molecule. Tungsten oxides (WOx), transition metal oxides with high work functions and good stability, cast light on solving this problem. By a low-cost, scalable and high-throughput manufacturing process, herein the facile synthesis of a WOx solution and its doping in poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS + WOx) is systematically investigated for assembling efficient UV OLEDs. X-ray diffraction, atomic force microscopy, scanning electron microscopy and X-ray photoelectron spectroscopy measurements confirm that WOx and PEDOT:PSS + WOx have good film morphology and exceptional electronic properties, such as the oxygen deficiency dominated non-stoichiometry of WOx. With PEDOT:PSS + WOx tailoring hole injection and 2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole as the emitter, the UV OLEDs show outstanding electro-optic performance, with a radiance of 3.98 mW cm-2, external quantum efficiency of 2.30%, electroluminescence peak at 400 nm and full width at half maximum of 47 nm, which is superior to the performance of the corresponding reference materials. The mechanism of charge transfer from the PEDOT polycation to WOx, enhancing conductivity, is responsible for the robust hole injection/transport and is further elucidated by ultraviolet photoelectron spectroscopy and impedance spectroscopy, contributing to the optimization of the carrier balance and recombination zone. Our results illustrate an alternative approach for boosting UV OLED performance and advancing organic electronics.

The visible and ultraviolet organic light-emitting diodes with germanium dioxide as facile solution-processed anode buffer layer

Germanium dioxide (GeO2) aqueous solutions are facilely prepared and the corresponding anode buffer layers (ABLs) with solution process are demonstrated. Atomic force microscopy, X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy measurements show that solution-processed GeO2 behaves superior film morphology and enhanced work function. Using GeO2 as ABL of organic light-emitting diodes (OLEDs), the visible device with tris(8-hydroxy-quinolinato)aluminium as emitter gives maximum luminous efficiency of 6.5 cd/A and power efficiency of 3.5 lm/W, the ultraviolet device with 3-(4-biphenyl)-4-phenyl-5-tert-butylphenyl-1,2,4-triazole as emitter exhibits short-wavelength emission with peak of 376 nm, full-width at half-maximum of 42 nm, maximum radiance of 3.36 mW/cm2 and external quantum efficiency of 1.5%. The performances are almost comparable to the counterparts with poly (3,4-ethylenedioxythiophene):poly (styrenesulfonate) as ABL. The current, impedance, phase and capacitance as a function of voltage characteristics elucidate that the GeO2 ABL formed from appropriate concentration of GeO2 aqueous solution favors hole injection enhancement and accordingly promoting device performance.

Sol-gel processed vanadium oxide as efficient hole injection layer in visible and ultraviolet organic light-emitting diodes

Low-cost, high-throughput and scalable production currently boosts organic electronic device towards solution processing. Sol-gel processed aqueous vanadium oxide (h-VOx) is facilely synthesized and proven to be efficient hole injection layer (HIL) in visible and ultraviolet organic light-emitting diodes (OLEDs). Atomic force microscopy and X-ray/ultraviolet photoelectron spectroscopy measurements indicate that h-VOx behaves superior film morphology and exceptional electronic properties such as oxygen vacancy dominated non-stoichiometry and appropriate surface work function. With tris(8-hydroxy-quinolinato)aluminium as emitter, the visible OLED gives maximum luminous and power efficiencies of 6.3 cd/A and 3.2 lm/W, respectively, which are slightly superior to the counterpart with vacuum thermally-evaporated VOx (5.6 cd/A and 2.7 lm/W). With 3-(4-biphenyl)-4-phenyl-5-tert-butylphenyl-1,2,4-triazole as emitter, the ultraviolet OLED produces attractive short-wavelength emission of 379 nm with full width at half maximum of 40 nm and improved durability. The maximum radiance and external quantum efficiency reach 15.3 mW/cm2 and 2.92%, respectively, which are considerably enhanced in comparison with the corresponding reference (11.9 mW/cm2 and 2.32%). Current versus voltage characteristics and impedance spectroscopy analysis elucidate that h-VOx exhibits robust hole injection and accordingly high-performance OLEDs. Our results pave an alternative way for advancing organic electronic devices and VOx applications with solution process.

Facile synthesis of solution-processed MoS2nanosheets and their application in high-performance ultraviolet organic light-emitting diodes

High-performance ultraviolet organic light-emitting diodes are assembled using liquid-phase exfoliated MoS2and its composites, MoS2–UVO and MoS2+PEDOT:PSS.

Effect of seed layers on low-temperature, chemical bath deposited ZnO nanorods-based near UV-OLED performance

Low-temperature wet chemical bath deposition (CBD) method is one of the most efficient and least hazardous solution-based techniques which is widely employed to grow ZnO NRs. In CBD method, a seed layer is usually deposited on the substrate. In this paper, high quality ZnO and aluminum doped ZnO (AZO) seed layers are sputtered on the indium tin oxide (ITO) coated glass. In continue, aligned ZnO NRs are grown on the AZO and ZnO seed layers via CBD technique. The effect of the growth time and seed layer on the physical properties of as-grown ZnO NRs are investigated. According to the results, the seed layer plays an essential role on the growth orientation and growth rate of the ZnO NRs. The ZnO NRs grown on AZO seed layer are more aligned rather than ZnO seed layer due to their higher texture coefficients. The relative photoluminescence (PL) intensity ratio of near band emission (NBE) to deep level emission (DLE) (INBE/IDLE) for the ZnO NRs grown on AZO and ZnO seed layers are calculated as 7.45 and 2.62, respectively. To investigate the performance of the as-grown ZnO NRs, near ultraviolet organic light-emitting diodes (UV-OLEDs) using ZnO NRs array as n-type material and poly [2-methoxy-5-(2-ethyl-hexyloxy)-1,4-phenylene-vinylene] (MEH-PPV) conjugated polymer as p-type material have been fabricated. The total concentration of traps (Nt), the characteristic energies (Et) and the turn-on voltages for the devices with the structures of ITO/AZO/ZnO NRs/MEH-PPV/Al (device A) and ITO/ZnO/ZnO NRs/MEH-PPV/Al (device B) are attained 7.65 × 1016 and 7.75 × 1016cm−3, 0.232 and 0.206eV, 23 and 21V, respectively. Moreover, based on the electroluminescence (EL) spectra, the NBE peaks for device A and B are obtained nearly in the wavelengths of 382 and 388nm, respectively. Finally, various charge carrier transportation processes of prepared UV-OLEDs have been studied, systematically.