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http://dx.doi.org/10.3807/COPP.2020.4.3.161

Recent Progress in High-Luminance Quantum Dot Light-Emitting Diodes  

Rhee, Seunghyun (Department of Electrical and Computer Engineering, Inter-university Semiconductor Research Center (ISRC), Seoul National University)
Kim, Kyunghwan (Department of Electrical and Computer Engineering, Inter-university Semiconductor Research Center (ISRC), Seoul National University)
Roh, Jeongkyun (Department of Electrical Engineering, Pusan National University)
Kwak, Jeonghun (Department of Electrical and Computer Engineering, Inter-university Semiconductor Research Center (ISRC), Seoul National University)
Publication Information
Current Optics and Photonics / v.4, no.3, 2020 , pp. 161-173 More about this Journal
Abstract
Colloidal quantum dots (QDs) have gained tremendous attention as a key material for highly advanced display technologies. The performance of QD light-emitting diodes (QLEDs) has improved significantly over the past two decades, owing to notable progress in both material development and device engineering. The brightness of QLEDs has improved by more than three orders of magnitude from that of early-stage devices, and has attained a value in the range of traditional inorganic LEDs. The emergence of high-luminance (HL) QLEDs has induced fresh demands to incorporate the unique features of QDs into a wide range of display applications, beyond indoor and mobile displays. Therefore it is necessary to assess the present status and prospects of HL-QLEDs, to expand the application domain of QD-based light sources. As part of this study, we review recent advances in HL-QLEDs. In particular, based on reports of brightness exceeding 105 cd/㎡, we have summarized the major approaches toward achieving high brightness in QLEDs, in terms of material development and device engineering. Furthermore, we briefly introduce the recent progress achieved toward QD laser diodes, being the next step in the development of HL-QLEDs. This review provides general guidelines for achieving HL-QLEDs, and reveals the high potential of QDs as a universal material solution that can enable realization of a wide range of display applications.
Keywords
Quantum dots; High luminance; QLED; QD laser diode;
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1 Y. Shang and Z. Ning, "Colloidal quantum-dots surface and device structure engineering for high-performance light-emitting diodes," Natl. Sci. Rev. 4, 170-183 (2017).   DOI
2 M. K. Choi, J. Yang, T. Hyeon, and D.-H. Kim, "Flexible quantum dot light-emitting diodes for next-generation displays," npj Flexible Electron. 2, 10 (2018).   DOI
3 F. Chen, Z. Guan, and A. Tang, "Nanostructure and device architecture engineering for high-performance quantum-dot light-emitting diodes," J. Mater. Chem. C 6, 10958-10981 (2018).   DOI
4 V. L. Colvin, M. C. Schlamp, and A. P. Alivisatos, "Light-emitting-diodes made from cadmium selenide nanocrystals and a semiconducting polymer," Nature 370, 354-357 (1994).   DOI
5 S. Coe, W. K. Woo, M. Bawendi, and V. Bulovic, "Electroluminescence from single monolayers of nanocrystals in molecular organic devices," Nature 420, 800-803 (2002).   DOI
6 A. H. Mueller, M. A. Petruska, M. Achermann, D. J. Werder, E. A. Akhadov, D. D. Koleske, M. A. Hoffbauer, and V. I. Klimov, "Multicolor light-emitting diodes based on semiconductor nanocrystals encapsulated in GaN charge injection layers," Nano Lett. 5, 1039-1044 (2005).   DOI
7 X. Dai, Z. Zhang, Y. Jin, Y. Niu, H. Cao, X. Liang, L. Chen, J. Wang, and X. Peng, "Solution-processed, high-performance light-emitting diodes based on quantum dots," Nature 515, 96-99 (2014).   DOI
8 J. Lim, S. Jun, E. Jang, H. Baik, H. Kim, and J. Cho, "Preparation of highly luminescent nanocrystals and their application to light-emitting diodes," Adv. Mater. 19, 1927-1932 (2007).   DOI
9 Q. Huang, J. Pan, Y. Zhang, J. Chen, Z. Tao, C. He, K. Zhou, Y. Tu, and W. Lei, "High-performance quantum dot light-emitting diodes with hybrid hole transport layer via doping engineering," Opt. Express 24, 25955-25963 (2016).   DOI
10 D. Y. Kondakov, W. C. Lenhart, and W. F. Nichols, "Operational degradation of organic light-emitting diodes: Mechanism and identification of chemical products," J. Appl. Phys. 101, 024512 (2007).   DOI
11 S. Schmidbauer, A. Hohenleutner, and B. Konig, "Chemical degradation in organic light-emitting devices: mechanisms and implications for the design of new materials," Adv. Mater. 25, 2114-2129 (2013).   DOI
12 K. Yoshida, T. Matsushima, Y. Shiihara, H. Kuwae, J. Mizuno, and C. Adachi, "Joule heat-induced breakdown of organic thin-film devices under pulse operation," J. Appl. Phys. 121, 195503 (2017).   DOI
13 G. W. Park, S. J. Lee, and J. H. Ko, "Comparison of out-coupling efficiency between bottom-emission and top-emission organic light-emitting diodes using FDTD simulation," J. Nanoelectron. Optoelectron. 11, 229-233 (2016).   DOI
14 Y. Zhao, C. Riemersma, F. Pietra, R. Koole, C. D. Donega, and A. Meijerink, "High-temperature luminescence quenching of colloidal quantum dots," ACS Nano 6, 9058-9067 (2012).   DOI
15 Q. Yue, W. Li, F. Kong, and K. Li, "Enhancing the out-coupling efficiency of organic light-emitting diodes using two-dimensional periodic nanostructures," Adv. Mater. Sci. Eng. 2012, 985762 (2012).
16 W. D. Kim, D. Kim, D.-E. Yoon, H. Lee, J. Lim, W. K. Bae, and D. C. Lee, "Pushing the efficiency envelope for semiconductor nanocrystal-based electroluminescence devices using anisotropic nanocrystals," Chem. Mater. 31, 3066-3082 (2019).   DOI
17 S. Hofmann, M. Thomschke, B. Lussem, and K. Leo, "Top-emitting organic light-emitting diodes," Opt. Express 19, A1250-A1264 (2011).   DOI
18 V. I. Klimov, A. A. Mikhailovsky, S. Xu, A. Malko, J. A. Hollingsworth, C. A. Leatherdale, H. J. Eisler, and M. G. Bawendi, "Optical gain and stimulated emission in nanocrystal quantum dots," Science 290, 314-317 (2000).   DOI
19 W. K. Bae, J. Lim, D. Lee, M. Park, H. Lee, J. Kwak, K. Char, C. Lee, and S. Lee, "R/G/B/natural white light thin colloidal quantum dot-based light-emitting devices," Adv. Mater. 26, 6387-6393 (2014).   DOI
20 C. Jiang, H. Liu, B. Liu, Z. Zhong, J. Zou, J. Wang, L. Wang, J. Peng, and Y. Cao, "Improved performance of inverted quantum dots light emitting devices by introducing double hole transport layers," Org. Electron. 31, 82-89 (2016).   DOI
21 J. Kwak, W. K. Bae, D. Lee, I. Park, J. Lim, M. Park, H. Cho, H. Woo, D. Y. Yoon, K. Char, S. Lee, and C. Lee, "Bright and efficient full-color colloidal quantum dot lightemitting diodes using an inverted device structure," Nano Lett. 12, 2362-2366 (2012).   DOI
22 S. J. Lim, M. U. Zahid, P. Le, L. Ma, D. Entenberg, A. S. Harney, J. Condeelis, and A. M. Smith, "Brightness-equalized quantum dots," Nat. Commun. 6, 8210 (2015).   DOI
23 J. Lim, Y. S. Park, K. Wu, H. J. Yun, and V. I. Klimov, "Droop-free colloidal quantum dot light-emitting diodes," Nano Lett. 18, 6645-6653 (2018).   DOI
24 H. Shen, Q. Gao, Y. Zhang, Y. Lin, Q. Lin, Z. Li, L. Chen, Z. Zeng, X. Li, Y. Jia, S. Wang, Z. L. Du, L. S. Li, and Z. Zhang, "Visible quantum dot light-emitting diodes with simultaneous high brightness and efficiency," Nat. Photonics 13, 192-197 (2019).   DOI
25 Y. Yang, Y. Zheng, W. Cao, A. Titov, J. Hyvonen, J. R. Manders, J. Xue, P. H. Holloway, and L. Qian, "High-efficiency light-emitting devices based on quantum dots with tailored nanostructures," Nat. Photonics 9, 259-266 (2015).   DOI
26 S. Rhee, J. H. Chang, D. Hahm, K. Kim, B. G. Jeong, H. J. Lee, J. Lim, K. Char, C. Lee, and W. K. Bae, ""Positive incentive" approach to enhance the operational stability of quantum dot-based light-emitting diodes," ACS Appl. Mater. Interfaces 11, 40252-40259 (2019).   DOI
27 J. Song, O. Wang, H. Shen, Q. Lin, Z. Li, L. Wang, X. Zhang, and L. S. Li, "Over 30% external quantum efficiency light-emitting diodes by engineering quantum dot-assisted energy level match for hole transport layer," Adv. Funct. Mater. 29, 1808377 (2019).   DOI
28 X. Li, Y.-B. Zhao, F. Fan, L. Levina, M. Liu, R. Quintero-Bermudez, X. Gong, L. N. Quan, J. Fan, Z. Yang, S. Hoogland, O. Voznyy, Z.-H. Lu, and E. H. Sargent, "Bright colloidal quantum dot light-emitting diodes enabled by efficient chlorination," Nat. Photonics 12, 159-164 (2018).   DOI
29 D. Kim, Y. Fu, S. Kim, W. Lee, K.-H. Lee, H. K. Chung, H.-J. Lee, H. Yang, and H. Chae, "Polyethylenimine ethoxylated-mediated all-solution-processed high-performance flexible inverted quantum dot-light-emitting device," ACS Nano 11, 1982-1990 (2017).   DOI
30 J. Li, Z. Liang, Q. Su, H. Jin, K. Wang, G. Xu, and X. Xu, "Small molecule-modified hole transport layer targeting low turn-on-voltage, bright, and efficient full-color quantum dot light emitting diodes," ACS Appl. Mater. Interfaces 10, 3865-3873 (2018).   DOI
31 G. Liu , X. Zhou, and S. Chen, "Very bright and efficient microcavity top-emitting quantum dot light-emitting diodes with Ag electrodes," ACS Appl. Mater. Interfaces 8, 16768-16775 (2016).   DOI
32 J. H. Oh, D. B. Choi, K. H. Lee, H. Yang, and Y. R. Do, "Enhanced light extraction from green quantum dot light-emitting diodes by attaching microstructure arrayed films," IEEE J. Sel. Top. Quantum Electron. 22, 42-47 (2016).
33 Y. Sun, Q. Su, H. Zhang, F. Wang, S. Zhang, and S. Chen, "Investigation on thermally induced efficiency roll-off: toward efficient and ultrabright quantum-dot light-emitting diodes," ACS Nano 13, 11433-11442 (2019).   DOI
34 K. Ding, Y. Fang, S. Dong, H. Chen, B. Luo, K. Jiang, H. Gu, L. Fan, S. Liu, B. Hu, and L. Wang, "24.1% external quantum efficiency of flexible quantum dot light-emitting diodes by light extraction of silver nanowire transparent electrodes," Adv. Opt. Mater. 6, 1800347 (2018).   DOI
35 B. S. Mashford, M. Stevenson, Z. Popovic, C. Hamilton, Z. Zhou, C. Breen, J. Steckel, V. Bulovic, M. Bawendi, S. Coe-Sullivan, and P. T. Kazlas, "High-efficiency quantum-dot light-emitting devices with enhanced charge injection," Nat. Photonics 7, 407-412 (2013).   DOI
36 L. Wang, J. Lin, Y. Hu, X. Guo, Y. Lv, Z. Tang, J. Zhao, Y. Fan, N. Zhang, Y. Wang, and X. Liu, "Blue quantum dot light-emitting diodes with high electroluminescent efficiency," ACS Appl. Mater. Interfaces 9, 38755-38760 (2017).   DOI
37 Y. Fu, W. Jiang, D. Kim, W. Lee, and H. Chae, "Highly efficient and fully solution-processed inverted light-emitting diodes with charge control interlayers," ACS Appl. Mater. Interfaces 10, 17295-17300 (2018).   DOI
38 Y.-H. Won, O. Cho, T. Kim, D.-Y. Chung, T. Kim, H. Chung, H. Jang, J. Lee, D. Kim, and E. Jang, "Highly efficient and stable InP/ZnSe/ZnS quantum dot light-emitting diodes," Nature 575, 634-638 (2019).   DOI
39 Y. Altintas, S. Genc, M. Y. Talpur, and E. Mutlugun, "CdSe/ZnS quantum dot films for high performance flexible lighting and display applications," Nanotechnology 27, 295604 (2016).   DOI
40 F. Fan, O. Voznyy, R. P. Sabatini, K. T. Bicanic, M. M. Adachi, J. R. McBride, K. R. Reid, Y. S. Park, X. Li, A. Jain, R. Quintero-Bermudez, M. Saravanapavanantham, M. Liu, M. Korkusinski, P. Hawrylak, V. I. Klimov, S. J. Rosenthal, S. Hoogland, and E. H. Sargent, "Continuous-wave lasing in colloidal quantum dot solids enabled by facet-selective epitaxy," Nature 544, 75-79 (2017).   DOI
41 J. Lim, Y.-S. Park, and V. I. Klimov, "Optical gain in colloidal quantum dots achieved with direct-current electrical pumping," Nat. Mater. 17, 42-49 (2018).   DOI
42 Y. S. Park, W. K. Bae, T. Baker, J. Lim, and V. I. Klimov, "Effect of auger recombination on lasing in heterostructured quantum dots with engineered core/shell interfaces," Nano Lett. 15, 7319-7328 (2015).   DOI
43 J. Roh, Y.-S. Park, J. Lim, and V. I. Klimov, "Optically pumped colloidal-quantum-dot lasing in LED-like devices with an integrated optical cavity," Nat. Commun. 11, 271 (2020).   DOI
44 J. Lim, B. G. Jeong, M. Park, J. K. Kim, J. M. Pietryga, Y.-S. Park, V. I. Klimov, C. Lee, D. C. Lee, and W. K. Bae, "Influence of shell thickness on the performance of light-emitting devices based on CdSe/Zn1-XCdXS core/shell heterostructured quantum dots," Adv. Mater. 26, 8034-8040 (2014).   DOI
45 W. K. Bae, K. Char, H. Hur, and S. Lee, "Single-step synthesis of quantum dots with chemical composition gradients," Chem. Mat. 20, 531-539 (2008).   DOI
46 H. Zhang, S. Chen, and X. W. Sun, "Efficient red/green/blue tandem quantum-dot light-emitting diodes with external quantum efficiency exceeding 21%," ACS Nano 12, 697-704 (2018).   DOI
47 Q. Su n, Y . A. Wang, L . S. L i, D . Wang, T. Z hu , J. X u, C. Yang, and Y. Li, "Bright, multicoloured light-emitting diodes based on quantum dots," Nat. Photonics 1, 717-722 (2007).   DOI
48 O. V. Kozlov, Y.-S. Park, J. Roh, I. Fedin, T. Nakotte, and V. I. Klimov, "Sub-single-exciton lasing using charged quantum dots coupled to a distributed feedback cavity," Science 365, 672-675 (2019).   DOI
49 K.-S. Cho, E. K. Lee, W.-J. Joo, E. Jang, T.-H. Kim, S. J. Lee, S.-J. Kwon, J. Y. Han, B. K. Kim, B. L. Choi, and J. M. Kim, "High-performance crosslinked colloidal quantum-dot light-emitting diodes," Nat. Photonics 3, 341-345 (2009).   DOI
50 L. Qian, Y. Zheng, J. Xue, and P. H. Holloway, "Stable and efficient quantum-dot light-emitting diodes based on solution-processed multilayer structures," Nat. Photonics 5, 543-548 (2011).   DOI
51 J.-M. Caruge, J. E. Halpert, V. Bulovic, and M. G. Bawendi, "NiO as an inorganic hole-transporting layer in quantum-dot light-emitting devices," Nano Lett. 6, 2991-2994 (2006).   DOI
52 X. Peng, M. C. Schlamp, A. V. Kadavanich, and A. P. Alivisatos, "Epitaxial growth of highly luminescent CdSe/CdS core/shell nanocrystals with photostability and electronic accessibility," J. Am. Chem. Soc. 119, 7019-7029 (1997).   DOI
53 H. Shen, W. Cao, N. T. Shewmon, C. Yang, L. S. Li, and J. Xue, "High-efficiency, low turn-on voltage blue-violet quantum-dot-based light-emitting diodes," Nano Lett. 15, 1211-1216 (2015).   DOI
54 H. Zhang, X. Sun, and S. Chen, "Over 100 cd $A^{-1}$ efficient quantum dot light-emitting diodes with inverted tandem structure," Adv. Funct. Mater. 27, 1700610 (2017).   DOI
55 B. O. Dabbousi, J. Rodriguez-Viejo, F. V. Mikulec, J. R. Heine, H . Mattou si, R. O ber, K . F. J ensen, a nd M . G. Bawendi, "(CdSe) ZnS core-shell quantum dots: synthesis and characterization of a size series of highly luminescent nanocrystallites," J. Phys. Chem. B 101, 9463-9475 (1997).   DOI
56 W. K. Bae, L. A. Padilha, Y. S. Park, H. McDaniel, I. Robel, J. M. Pietryga, and V. I. Klimov, "Controlled alloying of the core-shell interface in CdSe/CdS quantum dots for suppression of auger recombination," ACS Nano 7, 3411-3419 (2013).   DOI
57 D. V. Talapin, A. L. Rogach, A. Kornowski, M. Haase, and H. Weller, "Highly luminescent monodisperse CdSe and CdSe/ZnS nanocrystals synthesized in a hexadecylaminetrioctylphosphine oxide-trioctylphospine mixture," Nano Lett. 1, 207-211 (2001).   DOI
58 D. V. Talapin, I. Mekis, S. Gotzinger, A. Kornowski, O. Benson, and H. Weller, "CdSe/CdS/ZnS and CdSe/ZnSe/ZnS core-shell-shell nanocrystals," J. Phys. Chem. B 108, 18826-18831 (2004).   DOI
59 E. Jang, S. Jun, H. Jang, J. Llim, B. Kim, and Y. Kim, "White-light-emitting diodes with quantum dot color converters for display backlights," Adv. Mater. 22, 3076-3080 (2010).   DOI
60 R. Xie, U. Kolb, J. Li, T. Basche, and A. Mews, "Synthesis and characterization of highly luminescent CdSe-Core CdS/$Zn_{0.5}Cd_{0.5}S/ZnS$ multishell nanocrystals," J. Am. Chem. Soc. 127, 7480-7488 (2005).   DOI
61 J. Lim, M. Park, W. K. Bae, D. Lee, S. Lee, C. Lee, and K. Char, "Highly efficient cadmium-free quantum dot light-emitting diodes enabled by the direct formation of excitons within InP@ZnSeS qu antum dots," ACS Nano 7, 9019-9026 (2013).   DOI
62 R. E. Bailey and S. Nie, "Alloyed semiconductor quantum dots: Tuning the optical properties without changing the particle size," J. Am. Chem. Soc. 125, 7100-7106 (2003).   DOI
63 S. Dey, S. Chen, S. Thota, M. R. Shakil, S. L. Suib, and J. Zhao, "Effect of gradient alloying on photoluminescence blinking of single $CdS_xSe_{1-x}$ nanocrystals," J. Phys. Chem. C 120, 20547-20554 (2016).   DOI
64 Z. Li, Y. Hu, H. Shen, Q. Lin, L. Wang, H. Wang, W. Zhao, and L. S. Li, "Efficient and long-life green light-emitting diodes comprising tridentate thiol capped quantum dots," Laser Photon. Rev. 11, 1600227 (2017).   DOI
65 J. Zhang, Q. Yang, H. Cao, C. I. Ratcliffe, D. Kingston, Q. Y. Chen, J. Ouyang, X. Wu, D. M. Leek, F. S. Riehle, and K. Yu, "Bright gradient-alloyed $CdSexS_{1-x}$ quantum dots exhibiting cyan-blue emission," Chem. Mater. 28, 618-625 (2016).   DOI
66 D. Kim and D. C. Lee, "Surface ligands as permeation barrier in the growth and assembly of anisotropic semiconductor nanocrystals," J. Phys. Chem. Lett. 11, 2647-2657 (2020).   DOI
67 H. Lee, D.-E. Yoon, S. Koh, M. S. Kang, J. Lim, and D. C. Lee, "Ligands as a universal molecular toolkit in synthesis and assembly of semiconductor nanocrystals," Chem. Sci. 11, 2318-2329 (2020).   DOI
68 H. Zhang, J. Jang, W. Liu, and D. V. Talapin, "Colloidal nanocrystals with inorganic halide, pseudohalide, and halometallate ligands," ACS Nano 8, 7359-7369 (2014).   DOI
69 B.-H. Kang, J.-S. Lee, S.-W. Lee, S.-W. Kim, J.-W. Lee, S.-A. Gopalan, J.-S. Park, D.-H. Kwon, J.-H. Bae, H.-R. Kim, and S.-W. Kang, "Efficient exciton generation in atomic passivated CdSe/ZnS quantum dots light-emitting devices," Sci. Rep. 6, 34659 (2016).   DOI
70 J. H. Chang, P. Park, H. Jung, B. G. Jeong, D. Hahm, G. Nagamine, J. Ko, J. Cho, L. A. Padilha, D. C. Lee, C. Lee, K. Char, and W. K. Bae, "Unraveling the origin of operational instability of quantum dot based light-emitting diodes," ACS Nano 12, 10231-10239 (2018).   DOI
71 H. Shen, Q. Lin, W. Cao, C. Yang, N. T. Shewmon, H. Wang, J. Niu, L. S. Li, and J. Xue, "Efficient and long-lifetime full-color light-emitting diodes using high luminescence quantum yield thick-shell quantum dots," Nanoscale 9, 13583-13591 (2017).   DOI
72 C. Y. Han and H. Yang, "Development of colloidal quantum dots for electrically driven light-emitting devices," J. Korean Ceram. Soc. 54, 449-469 (2017).   DOI
73 W. K. Bae, Y. S. Park, J. Lim, D. Lee, L. A. Padilha, H. McDaniel, I. Robel, C. Lee, J. M. Pietryga, and V. I. Klimov, "Controlling the influence of Auger recombination on the performance of quantum-dot light-emitting diodes," Nat. Commun. 4, 2661 (2013).   DOI
74 J. M. Pietryga, Y.-S. Park, J. Lim, A. F. Fidler, W. K. Bae, S. Brovelli, and V. I. Klimov, "Spectroscopic and device aspects of nanocrystal quantum dots," Chem. Rev. 116, 10513-10622 (2016).   DOI
75 W. K. Bae and J. Lim, "Nanostructured colloidal quantum dots for efficient electroluminescence devices," Korean J. Chem. Eng. 36, 173-185 (2019).   DOI
76 Z. Li, "Enhanced performance of quantum dots light-emitting diodes: The case of $Al_2O_3$ electron blocking layer," Vacuum 137, 38-41 (2017).   DOI
77 X. Xiong, C. Wei, L. Xie, M. Chen, P. Tang, W. Shen, Z. Deng, X. Li, Y. Duan, W. Su, H. Zeng, and Z. Cui, "Realizing 17.0% external quantum efficiency in red quantum dot light-emitting diodes by pursuing the ideal inkjet-printed film and interface," Org. Electron. 73, 247-254 (2019).   DOI
78 Y. Lee, B. G. Jeong, H. Roh, J. Roh, J. Han, D. C. Lee, W. K. Bae, J. Y. Kim, and C. Lee, "Enhanced lifetime and efficiency of red quantum dot light-emitting diodes with Y-doped ZnO sol-gel electron-transport layers by reducing excess electron injection," Adv. Quantum Technol. 1, 1700006 (2018).   DOI
79 J.-H. Kim, C.-Y. Han, K.-H. Lee, K.-S. An, W. Song, J. Kim, M. S. Oh, Y. R. Do, and H. Yang, "Performance improvement of quantum dot-light-emitting diodes enabled by an alloyed ZnMgO nanoparticle electron transport layer," Chem. Mater. 27, 197-204 (2015).   DOI
80 X. Jin, C. Chang, W. Zhao, S. Huang, X. Gu, Q. Zhang, F. Li, Y. Zhang, and Q. Li, "Balancing the electron and hole transfer for efficient quantum dot light-emitting diodes by employing a versatile organic electron-blocking layer," ACS Appl. Mater. Interfaces 10, 15803-15811 (2018).   DOI
81 I. Cho, H. Jung, B. G. Jeong, J. H. Chang, Y. Kim, K. Char, D. C. Lee, C. Lee, J. Cho, and W. K. Bae, "Multifunctional dendrimer ligands for high efficiency, solution-processed quantum dot light-emitting diodes," ACS Nano 11, 684-692 (2017).   DOI
82 J.-R. Gong, L.-J. Wan, S.-B. Lei, C.-L. Bai, X.-H. Zhang, and S.-T. Lee, "Direct evidence of molecular aggregation and degradation mechanism of organic light-emitting diodes under joule heating: an STM and photoluminescence study," J. Phys. Chem. B 109, 1675-1682 (2005).   DOI