Name: Enhanced Electron Injection and Exciton Confinement for Pure Blue Quantum-Dot Light-Emitting Diodes by Introducing Partially Oxidized Aluminum Cathode (Video) | JoVE Journal
Uploaded: 2018-05-31T15:00:00.000+00:00
Duration: 10 min 41 s
Description: Learn to fabricate high-performance blue quantum-dot LEDs using a partially-oxidized aluminum cathode. This method enhances electron injection, improves color purity, and simplifies fabrication by eliminating additional electron-transport layers.

ai_agent_IP

ai_agent

maintenance

instantTrialDurationMinutes

isBiopharma

enableNewMyJoveSectionDesign

educationFeatures

seoMetaApi

ai_copilot_institution_blacklist

ai_chat_institution_blacklist

freeAccessWindow

ssoRoleCapture

scheduledMaintenanceBanner

joveLabsFeatures

disable_autoplay_for_bots

extended_trial_duration

5 minutes

This work was supported by the NSFC (51573042), The National Key Basic Research Program of China (973 project, 2015CB932201), Fundamental Research Funds for the Central Universities, China (JB2015RCJ02, 2016YQ06, 2016MS50, 2016XS47).

1. Pattern Etching of Indium Tin Oxide (ITO) Glass
<ol>
	<li>Cut large pieces of ITO glass (12 cm &#215; 12 cm) into 15 mm wide strips. Clean the ITO glass surface using a dust-free cloth with alcohol.</li>
	<li>Check the conductive side of the ITO glass with a digital multimeter. Cover the active area of the ITO glass with adhesive tape, so that the active area is 2 mm wide in the middle.</li>
	<li>Pour the zinc powder on the ITO glass (to a thickness of about 0.5 mm).</li>
	<li>Pour the hydrochloric acid solution (36 wt%) onto the surface of the ITO glass and allow the ITO glass to completely soak in hydrochloric acid solution, then etch for 15 s.</li>
	<li>Pour out the hydrochloric acid solution after corrosion, then rinse the ITO glass with water immediately. Remove the adhesive tape on the ITO glass.</li>
</ol>
2. Cleaning the ITO Glass
<ol>
	<li>Immerse the ITO glass in a petri dish containing acetone solution for 15 min. Wipe off the glue on the ITO glass using a cotton ball.</li>
	<li>Cut the ITO glass into square pieces (approximately 15 mm &#215; 15 mm) with a glass cutter.</li>
	<li>Sonicate the ITO glass sequentially in detergent water, tap water, deionized water, acetone, and isopropyl alcohol for 15 min.</li>
	<li>Blow-dry the ITO glass with nitrogen gas followed by drying in an oven at 150 &#176;C for 5 min in air atmosphere.</li>
	<li>Put the cleaned ITO glass into an ultraviolet-ozone chamber and treat for 15 min.</li>
</ol>
3. Fabrication of a Hole Injection Layer
<ol>
	<li>Take out the poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) solution from the refrigerator. Stir the PEDOT:PSS solution at room temperature for 20 min to obtain an evenly dispersed solution. 
	NOTE: The UV-Ozone treatment (Section 2.5) and agitation of PEDOT:PSS solution should be carried out simultaneously to avoid UV-Ozone treatment failure. Room temperature is maintained at 25 &#176;C.</li>
	<li>Take about 2 mL of PEDOT:PSS solution with a 10 mL syringe, and install a 0.45 &#181;m polyether sulfone (PES) filter on the syringe.</li>
	<li>Place the ITO glass at the center of the spin-coater. Pour two drops of the PEDOT:PSS solution onto the ITO glass.</li>
	<li>Spin-coat the filtered PEDOT:PSS solution on the ITO substrate at 3,000 rpm for 30 s and then anneal the PEDOT:PSS-coated ITO at 150 &#176;C for 15 min to give a 30 nm PEDOT:PSS film.</li>
</ol>
4. Fabrication of a Hole Transport Layer
NOTE: The hole transport layer and the emissive layer are fabricated in a nitrogen-filled glove-box with controlled oxygen and water concentration below 50 ppm.
<ol>
	<li>Dissolve poly(N,N&#8242;-bis(4-butylphenyl)-N,N&#8242;-bis(phenyl)-benzidine) (Poly-TPD) in o-dichlorobenzene (1 mL) with a concentration of 25 mg mL-1. Stir at room temperature overnight in the nitrogen-filled glove-box.</li>
	<li>Pour 35 &#181;L of Poly-TPD solution onto the PEDOT:PSS-coated ITO. Spin-coat the Poly-TPD solution at 3,000 rpm for 30 s to give a 40 nm Poly-TPD film, and then anneal at 150 &#176;C for 30 min.</li>
</ol>
5. Fabrication of an Emissive Layer
<ol>
	<li>Dissolve ZnCdS/ZnS quantum dots in toluene solution (300 &#181;L) with a concentration of 14.3 mg mL-1.</li>
	<li>Pour 35 &#181;L of the ZnCdS/ZnS solution onto the top of the Poly-TPD. Spin-coat the ZnCdS/ZnS solution at 3,000 rpm for 30 s to give a 40 nm film. 
	NOTE: Baking is not necessary.</li>
</ol>
6. Vacuum Deposition
<ol>
	<li>After a pressure of 10-4 Pa is reached, deposit the aluminum Tris(8-Hydroxyquinolinate) (Alq3) on the substrates with a rate of 0.3 &#197; s-1 in a thermal evaporation chamber to give a 15 nm Alq3 film. 
	NOTE: The Alq3 is deposited only for the device structure of ITO/PEDOT:PSS/Poly-TPD/QDs/Alq3/Al.</li>
	<li>Scrape a 2 mm wide active layer with a scraper to expose the ITO glass substrate.</li>
	<li>Place the substrates in a metal mask and transfer them into a thermal evaporation chamber. Deposit the aluminum electrode with a rate of 1 &#197; s-1 to give a 100 nm Al film.</li>
</ol>
7. Autoxidation Procedure
<ol>
	<li>Transfer the as-prepared Al cathode into a vacuum oven, and then pump air out of the oven until it is almost a vacuum.</li>
	<li>Open the deflation valve and inject anhydrous compound air (O2=20%, N2=80%) into the vacuum oven with a pressure of 3 &#215; 104 Pa. Oxidize for 0, 4.5, 12, and 17 h at room temperature (in the oven).</li>
</ol>

<ol><li>Shirasaki, Y., Supran, G. J., Bawendi, M. G., Bulović, V. <a target="_blank" href="https://www.nature.com/articles/nphoton.2012.328">Emergence of colloidal quantum-dot light-emitting technologies.</a> Nat. Photonics. 7 (1), 13-23 (2012).</li>
<li>Chen, O., Wei, H., Maurice, A., Bawendi, M., Reiss, P. <a target="_blank" href="https://www.cambridge.org/core/journals/mrs-bulletin/article/pure-colors-from-coreshell-quantum-dots/4B8AC6E7E8B1B554420EE8702AC724E5">Pure colors from core-shell quantum dots.</a> MRS Bull. 38 (09), 696-702 (2013).</li>
<li>Dai, X., Deng, Y., Peng, X., Jin, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Quantum-Dot+Light-Emitting+Diodes+for+Large-Area+Displays%3A+Towards+the+Dawn+of+Commercialization%5BTitle%5D)+AND+%22Adv.+Mater%22%5BJournal%5D)">Quantum-Dot Light-Emitting Diodes for Large-Area Displays: Towards the Dawn of Commercialization.</a> Adv. Mater. 29 (14), (2017).</li>
<li>Wang, L., et al. <a target="_blank" href="http://www.sciencedirect.com/science/article/pii/S1566119916302890">High-performance azure blue quantum dot light-emitting diodes via doping PVK in emitting layer.</a> Org. Electron. 37, 280-286 (2016).</li>
<li>Colvin, V., Schlamp, M., Alivisatos, A. P. <a target="_blank" href="https://www.nature.com/articles/370354a0">Light-emitting diodes made from cadmium selenide nanocrystals and a semiconducting polymer.</a> Nature. 370 (6488), 354-357 (1994).</li>
<li>Tan, Z., et al. <a target="_blank" href="http://aip.scitation.org/doi/abs/10.1063/1.3074335">Colloidal nanocrystal-based light-emitting diodes fabricated on plastic toward flexible quantum dot optoelectronics.</a> J. Appl. Phys. 105 (03), 034312(2009).</li>
<li>Tan, Z., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Bright+and+color-saturated+emission+from+blue+light-emitting+diodes+based+on+solution-processed+colloidal+nanocrystal+quantum+dots%5BTitle%5D)+AND+%22Nano+Lett%22%5BJournal%5D)">Bright and color-saturated emission from blue light-emitting diodes based on solution-processed colloidal nanocrystal quantum dots.</a> Nano Lett. 7 (12), 3803-3807 (2007).</li>
<li>Lee, C. -L., Nam, S. -W., Kim, V., Kim, J. -J., Kim, K. -B. <a target="_blank" href="http://onlinelibrary.wiley.com/doi/10.1002/pssb.200880609/abstract">Electroluminescence from monolayer of quantum dots formed by multiple dip-coating processes.</a> physica status solidi (b). 246, 803-807 (2009).</li>
<li>Lee, T. -C., et al. <a target="_blank" href="http://onlinelibrary.wiley.com/doi/10.1002/adfm.200900233/abstract">Rational Design of Charge-Neutral, Near-Infrared-Emitting Osmium(II) Complexes and OLED Fabrication.</a> Advanced Functional Materials. 19, 2639-2647 (2009).</li>
<li>Qian, L., Zheng, Y., Xue, J., Holloway, P. H. <a target="_blank" href="https://www.nature.com/articles/nphoton.2011.171">Stable and efficient quantum-dot light-emitting diodes based on solution-processed multilayer structures.</a> Nat. Photonics. 5 (9), 543-548 (2011).</li>
<li>Kwak, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Bright+and+efficient+full-color+colloidal+quantum+dot+light-emitting+diodes+using+an+inverted+device+structure%5BTitle%5D)+AND+%22Nano+Lett%22%5BJournal%5D)">Bright and efficient full-color colloidal quantum dot light-emitting diodes using an inverted device structure.</a> Nano Lett. 12 (5), 2362-2366 (2012).</li>
<li>Dai, X., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Solution-processed%2C+high-performance+light-emitting+diodes+based+on+quantum+dots%5BTitle%5D)+AND+%22Nature%22%5BJournal%5D)">Solution-processed, high-performance light-emitting diodes based on quantum dots.</a> Nature. 515 (7525), 96-99 (2014).</li>
<li>Lee, K. -H., Lee, J. -H., Song, W. -S., Ko, H., Lee, C., Lee, J. -H., Yang, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Highly+efficient%2C+color-pure%2C+color-stable%2C+blue+quantum+dots+light-emitting+devices%5BTitle%5D)+AND+%22ACS+Nano%22%5BJournal%5D)">Highly efficient, color-pure, color-stable, blue quantum dots light-emitting devices.</a> ACS Nano. 7 (8), 7295-7302 (2013).</li>
<li>Shen, H., et al. <a target="_blank" href="http://onlinelibrary.wiley.com/doi/10.1002/adfm.201302964/abstract">High-efficient deep-blue light-emitting diodes by using high quality ZnxCd1-xS/ZnS core/shell quantum dots.</a> Adv. Funct. Mater. 24 (16), 2367-2373 (2014).</li>
<li>Wang, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Bright%2C+efficient%2C+and+color-stable+violet+ZnSe-based+quantum+dot+light-emitting+diodes%5BTitle%5D)+AND+%22Nanoscale%22%5BJournal%5D)">Bright, efficient, and color-stable violet ZnSe-based quantum dot light-emitting diodes.</a> Nanoscale. 7 (7), 2951-2959 (2015).</li>
<li>Shen, H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((High-efficiency%2C+low+turn-on+voltage+blue-violet+quantum-dot-based+light-emitting+diodes%5BTitle%5D)+AND+%22Nano+Lett%22%5BJournal%5D)">High-efficiency, low turn-on voltage blue-violet quantum-dot-based light-emitting diodes.</a> Nano Lett. 15 (2), 1211-1216 (2015).</li>
<li>Fokina, A., et al. <a target="_blank" href="http://onlinelibrary.wiley.com/doi/10.1002/admi.201600279/full">The role of emission layer morphology on the enhanced performance of light-emitting diodes based on quantum dot-semiconducting polymer hybrids.</a> Adv. Mater. Interfaces. 3 (18), 1600279(2016).</li>
<li>Yang, Y., et al. <a target="_blank" href="https://www.nature.com/articles/nphoton.2015.36">High-efficiency light-emitting devices based on quantum dots with tailored nanostructures.</a> Nat. Photonics. 9, 259-266 (2015).</li>
<li>Cheng, T., et al. <a target="_blank" href="http://onlinelibrary.wiley.com/doi/10.1002/adom.201700035/abstract">Pure Blue and Highly Luminescent Quantum-Dot Light-Emitting Diodes with Enhanced Electron Injection and Exciton Confinement via Partially Oxidized Aluminum Cathode.</a> Adv. Opt. Mater. 5 (11), 1700035(2017).</li>
<li>Rotole, J. A., Sherwood, P. M. A. <a target="_blank" href="http://avs.scitation.org/doi/abs/10.1116/1.1247852">Gamma-Alumina (γ-Al2O3) by XPS.</a> Surf. Sci. Spectra. 5 (1), 18-24 (1998).</li>
<li>Liu, J., Yang, W., Li, Y., Fan, L., Li, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Electrochemical+studies+of+the+effects+of+the+size%2C+ligand+and+composition+on+the+band+structures+of+CdSe%2C+CdTe+and+their+alloy+nanocrystals%5BTitle%5D)+AND+%22Phys.+Chem.+Chem.+Phys%22%5BJournal%5D)">Electrochemical studies of the effects of the size, ligand and composition on the band structures of CdSe, CdTe and their alloy nanocrystals.</a> Phys. Chem. Chem. Phys. 16 (10), 4778-4788 (2014).</li>
<li>Abbaszadeh, D., Wetzelaer, G. A. H., Doumon, N. Y., Blom, P. W. M. <a target="_blank" href="http://aip.scitation.org/doi/abs/10.1063/1.4943190">Efficient polymer light-emitting diode with air-stable aluminum cathode.</a> J. Appl. Phys. 119 (9), 095503(2016).</li>
<li>Yu, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Optimization+of+the+energy+level+alignment+between+the+photoactive+layer+and+the+cathode+contact+utilizing+solution-processed+hafnium+acetylacetonate+as+buffer+layer+for+efficient+polymer+solar+cells%5BTitle%5D)+AND+%22Acs+Appl.+Mater.+Interfaces%22%5BJournal%5D)">Optimization of the energy level alignment between the photoactive layer and the cathode contact utilizing solution-processed hafnium acetylacetonate as buffer layer for efficient polymer solar cells.</a> Acs Appl. Mater. Interfaces. 8 (1), 432-441 (2016).</li>
<li>Li, F., Tang, H., Anderegg, J., Shinar, J. <a target="_blank" href="http://aip.scitation.org/doi/abs/10.1063/1.118539">Fabrication and electroluminescence of double-layered organic light-emitting diodes with the Al2O3/Al cathode.</a> J. Shinar, Appl. Phys. Lett. 70 (10), 1233-1235 (1997).</li>
<li>Bai, Z., et al. <a target="_blank" href="http://pubs.acs.org/doi/abs/10.1021/acs.chemmater.5b04480">Hydroxyl-Terminated CuInS2 Based Quantum Dots: Toward Efficient and Bright Light Emitting Diodes.</a> Chemistry of Materials. 28, 1085-1091 (2016).</li>
<li>Wang, Z., et al. <a target="_blank" href="http://pubs.acs.org/doi/abs/10.1021/acs.jpcc.7b11518">Efficient and Stable Pure Green All-Inorganic Perovskite CsPbBr3 Light-Emitting Diodes with a Solution-Processed NiOx Interlayer.</a> The Journal of Physical Chemistry C. , (2017).</li>
</ol>

We have nothing to disclose.

The device architecture of the blue QD-LED consists of an ITO transparent anode, a PEDOT:PSS HIL (30 nm), a Poly-TPD HTL (40 nm), a ZnCdS/ZnS QDs EML (40 nm), and an Al:Al2O3 cathode (100 nm). Due to the porous character of the Al cathode, we obtained an oxidized Al cathode by exposing it to oxygen. Figure 2e and Figure 2f display the energy level alignment diagrams of QDs layer with Al and Al:Al2O3. When the QDs conta...

Light-emitting diodes (LEDs) based on colloidal semiconductor quantum dots have attracted great interest due to their unique advantages, including solution processability, tunable emission wavelength, excellent color purity, flexible fabrication, and low processing cost1,2,3,4. Since the first demonstrations of QDs-based LEDs in 1994, tremendous efforts have been devoted to engineering the materials and device structures5,6,7. A typical QD-LED device is designed to have a three-layered sandwich architecture which consists of a hole transport layer (HTL), an emissive layer, and an electron transport layer (ETL). The choice of a suitable charge transport layer is critical to balance the injected holes and electrons into the emissive layer for radiative recombination. Currently, vacuum-deposited small molecules are widely used as ETL, for instance, bathocuproine (BCP), tris(8-Hydroxyquinolinate) (Alq3), and 3-(biphenyl-4-yl)-5-(4-tertbutylphenyl)-4-phenyl-4H-1,2,4-triazole (TAZ)8. However, the unbalanced carrier injection often causes the recombination region shift to ETL, making unwanted parasitic electroluminescence (EL) emission and deteriorating the device performance9.
To enhance the device efficiency and environmental stability, solution-processed ZnO nanoparticles were introduced as an electron transport layer instead of the vacuum-deposited small-molecule materials. Highly bright RGB QD-LEDs were demonstrated for conventional device architecture, showing luminance up to 31,000, 68,000, and 4,200 cd m-2 for emission of orange-red, green, and blue, respectively10. For an inverted device architecture, high performance RGB QD-LEDs with low turn on voltage were successfully demonstrated with brightness and external quantum efficiencies (EQE) of 23,040 cd m-2 and 7.3% for red, 218,800 cd m-2 and 5.8% for green, and 2,250 cd m-2 and 1.7% for blue, respectively11. To balance the injected charges and preserve the QDs emissive layer, an insulating poly(methylmethacrylate) (PMMA) thin film was inserted between the QDs and ZnO ETL. The optimized deep-red QD-LEDs exhibited high external quantum efficiencies up to 20.5% and a low turn-on voltage of only 1.7 V12.
Besides, optimizing the optoelectronic properties and nanostructures of QDs also plays a crucial role in boosting the device performance. For instance, highly fluorescent blue QDs with photoluminescence quantum yield (PLQE) up to 98% were synthesized through optimizing the ZnS shelling time13. Similarly, high-quality, violet-blue QDs with near 100% PLQE were synthesized by precisely controlling the reaction temperature. The violet-blue QDs-LED devices showed remarkable luminance and EQE up to 4,200 cd m-2 and 3.8%, respectively14. This synthesis method is also applicable to violet ZnSe/ZnS core/shell QDs, the QD-LEDs exhibited high luminance (2,632 cd m-2) and efficiency (EQE=7.83%) by using Cd-free QDs15. Since blue quantum dots with high PLQE have been demonstrated, high charge injection efficiency in the QDs layer plays another crucial role in fabricating high performance QD-LEDs. By substituting long chain oleic acid ligands to shorten 1-octanethiol ligands, the electron mobility of QDs film was increased two-fold, and a high EQE value over 10% was obtained16. The surface ligand exchange can also improve the morphology of QDs film and suppress the photoluminescence quenching among QDs. For instance, QDs-LED showed improved device performance by using chemically grafted QDs-semiconducting polymer hybrids17. Besides, high-performance QDs were prepared through reasonable optimization of the graded composition and thickness of the QDs shell, due to the enhanced charge injection, transport, and recombination18.
In this work, we introduced a partial autoxidized aluminum (Al) cathode to improve the performance of ZnCdS/ZnS graded core/shell-based blue QD-LEDs19. The change of the potential energy barrier of the Al cathode was confirmed by ultraviolet photoelectron spectroscopy (UPS) and X-ray photoelectron spectroscopy (XPS). Furthermore, the fast charge carrier dynamics at the QDs/Al and QDs/Al:Al2O3 interface were analyzed by time-resolved photoluminescence (TRPL) measurements. In order to further validate the influence of partially oxidized Al on device performance, QD-LEDs with different cathodes (Al only, Al:Al2O3, Al2O3/Al, Al2O3/Al:Al2O3, and Alq3/Al) were fabricated. As a result, high performance pure blue QD-LEDs were demonstrated by employing Al:Al2O3 cathodes, with a maximum luminance of 13,002 cd m-2 and a peak current efficiency of 1.15 cd A-1. Furthermore, there was no additional organic ETL involved in the device architecture, which can avoid unwanted parasitic EL to guarantee the color purity under different working voltages.

<table><tbody><tr><td>Indium Tin Oxide (ITO)-coated glass&lt;br/&gt; substrate</td><td>CSG Holding Co., Ltd.</td><td></td><td>Resistivity&amp;asymp;10 &amp;Omega;/sq</td></tr><tr><td>Zinc powder</td><td>Sigma-Aldrich</td><td>96454</td><td>Molecular Weight 65.38</td></tr><tr><td>Isopropyl alcohol</td><td>Beijing Chemical Reagent</td><td>67-63-0</td><td>Analytically pure</td></tr><tr><td>Toluene</td><td>Innochem</td><td>I01367</td><td>Analytically pure</td></tr><tr><td>Acetone</td><td>Innochem</td><td>I01366</td><td>Analytically pure</td></tr><tr><td>Hydrochloric acid</td><td>acros</td><td>124210025</td><td>1 N standard solution</td></tr><tr><td>O-dichlorobenzene</td><td>acros</td><td>396961000</td><td>98+%, Extra Dry</td></tr><tr><td>Poly(3,4-ethylenedioxythiophene) doped polystyrene sulfonate (PEDOT:PSS)</td><td>H. C.Stark</td><td>Clevious P VP Al 4083</td><td></td></tr><tr><td>Poly(N,N&amp;prime;-bis(4-butylphenyl)-N,N&amp;prime;-bis(phenyl)-benzidine) (Poly-TPD)</td><td>Luminescence Technology</td><td>LT-N149</td><td></td></tr><tr><td>Aluminum tris(8-Hydroxyquinolinate) (Alq&lt;sub&gt;3&lt;/sub&gt;)</td><td>Luminescence Technology</td><td>LT-E401</td><td></td></tr><tr><td>UV-O cleaner</td><td>Jelight Company</td><td>92618</td><td></td></tr><tr><td>Filter</td><td>Jinteng</td><td>JTSF0303/0304</td><td>Polyether sulfone (0.45 &amp;mu;m)</td></tr><tr><td>Ultrasonic cleaner</td><td>HECHUANG ULTRASONIC</td><td>KH-500DE</td><td></td></tr><tr><td>Digital multimeter</td><td>UNI-T</td><td>UT39A</td><td></td></tr><tr><td>Spin coater</td><td>IMECAS</td><td>KW-4A</td><td></td></tr><tr><td>Digital hotplate</td><td>Stuart</td><td>SD160</td><td></td></tr></tbody></table>

enhanced electron injection and exciton confinement for pure blue quantum-dot light-emitting diodes by introducing partially oxidized aluminum cathode

Enhanced Electron Injection and Exciton Confinement for Pure Blue Quantum-Dot Light-Emitting Diodes by Introducing Partially Oxidized Aluminum Cathode

Stable and efficient red (R), green (G), and blue (B) light sources based on solution-processed quantum dots (QDs) play important roles in next-generation displays and solid-state lighting technologies. The brightness and efficiency of blue QDs-based light-emitting diodes (LEDs) remain inferior to their red and green counterparts, due to the inherently unfavorable energy levels of different colors of light. To solve these problems, a device structure should be designed to balance the injection holes and electrons into the emissive QD layer. Herein, through a simple autoxidation strategy, pure blue QD-LEDs which are highly bright and efficient are demonstrated, with a structure of ITO/PEDOT:PSS/Poly-TPD/QDs/Al:Al2O3. The autoxidized Al:Al2O3 cathode can effectively balance the injected charges and enhance radiative recombination without introducing an additional electron transport layer (ETL). As a result, high color-saturated blue QD-LEDs are achieved with a maximum luminance over 13,000 cd m-2, and a maximum current efficiency of 1.15 cd A-1. The easily controlled autoxidation procedure paves the way for achieving high-performance blue QD-LEDs.

UV-Vis absorption and photoluminescence (PL) spectra were used to record the optical properties of ZnCdS/ZnS graded core/shell-based blue QDs. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) images were collected for the morphologies of QDs (Figure 1). X-ray photoelectron spectroscopy (XPS), electrochemical study, and ultraviolet photoelectron spectroscopy (UPS) were employed to detect the structural properties and energy levels ...

A protocol is presented for fabricating high-performance, pure blue ZnCdS/ZnS-based quantum dots light-emitting diodes by employing an autoxidized aluminum cathode.

Stable and efficient red (R), green (G), and blue (B) light sources based on solution-processed quantum dots (QDs) play important roles in next-generation ...

enhanced-electron-injection-exciton-confinement-for-pure-blue-quantum

Research

JoVE Journal

Engineering

We describe the preparation of colloidal quantum dots with minimized hydrodynamic size for single-molecule fluorescence imaging.  Compared to conventional quantum dots, these nanoparticles are similar in size to globular proteins and are optimized for single-molecule brightness, stability against photodegradation, and resistance to nonspecific binding to proteins and cells.

Compact Quantum Dots for Single-molecule Imaging

This paper presents a detailed fabrication protocol for gate-defined semiconductor lateral quantum dots on gallium arsenide heterostructures. These nanoscale devices are used to trap few electrons for use as quantum bits in quantum information processing or for other mesoscopic experiments such as coherent conductance measurements.

Nanofabrication of Gate-defined GaAs/AlGaAs Lateral Quantum Dots

The fabrication process and experimental characterization techniques relevant to single-electron pumps based on silicon metal-oxide-semiconductor quantum dots are discussed.

Silicon Metal-oxide-semiconductor Quantum Dots for Single-electron Pumping

An excellent chemical and luminescence stabilities of (oxy)nitride phosphors present it as an promising alternative to currently used sulfide and oxide phosphors. In this paper, we present the way to investigate its local luminescence properties using low-energy cathodoluminescence (CL).

Low-energy Cathodoluminescence for (Oxy)Nitride Phosphors

The authors present a method for fabricating stable white-light-emitting electrochemical cells utilizing emission from exciplexes formed between a blue-emitting fluorene polymer and aromatic amines.

Fabrication of White Light-emitting Electrochemical Cells with Stable Emission from Exciplexes

Resonant excitation of a single self-assembled quantum dot can be achieved using an excitation mode orthogonal to the fluorescence collection mode. We demonstrate a method using the waveguide and Fabry-Perot modes of a planar microcavity surrounding the quantum dots. The method allows complete freedom in the detection polarization.

Resonance Fluorescence of an InGaAs Quantum Dot in a Planar Cavity Using Orthogonal Excitation and Detection

Here, we present a method of the spectroscopic characterization of organic molecules by means of time-resolved photoluminescence spectroscopy on the nanosecond-to-millisecond timescale in oxygen-free conditions. Methods to efficiently remove oxygen from the samples and, thus, limit luminescence quenching are also described.

Time-resolved Photophysical Characterization of Triplet-harvesting Organic Compounds at an Oxygen-free Environment Using an iCCD Camera

A protocol for synthesizing inorganic-lead-halide hybrid perovskite quantum dot inks for inkjet printing and the protocol for preparing and printing the quantum dot inks in an inkjet printer with post characterization techniques are presented.

Inkjet Printing All Inorganic Halide Perovskite Inks for Photovoltaic Applications

A protocol for graphene-assisted growth of high-quality AlN films on nano-patterned sapphire substrate is presented.

Graphene-Assisted Quasi-van der Waals Epitaxy of AlN Film on Nano-Patterned Sapphire Substrate for Ultraviolet Light Emitting Diodes

Presented here is a protocol for the fabrication of efficient, simple, solution-deposited organic light-emitting diodes with low roll-off.

Development of Efficient OLEDs from Solution Deposition

Organic Light Emitting Diode (OLED) devices offer superior display quality with better contrast while propounding environmental benefits by lower energy consumption. Here, a simple strategy for the solution-processed OLED device fabrication is presented in a sequential manner.

Step-by-Step Guide for Harnessing Organic Light Emitting Diodes by Solution Processed Device Fabrication of a TADF Emitter

Learn to fabricate high-performance blue quantum-dot LEDs using a partially-oxidized aluminum cathode. This method enhances electron injection, improves color purity, and simplifies fabrication by eliminating additional electron-transport layers.

Enhanced Electron Injection and Exciton Confinement for Pure Blue Quantum-Dot Light-Emitting Diodes by Introducing Partially Oxidized Aluminum Cathode (Video) | JoVE Journal

Enhanced Electron Injection and Exciton Confinement for Pure Blue Quantum-Dot Light-Emitting Diodes by Introducing Partially Oxidized Aluminum Cathode

Explore More Videos