Composite Hole Transport Layer Consisting of High-Mobility Polymer and Small Molecule With Deep-Lying HOMO Level for Efficient Quantum Dot Light-Emitting Diodes

Zhao, Yongshuang; Chen, Lixiang; Wu, Jialin; Tan, Xinxin; Xiong, Zuhong; Lei, Yanlian

doi:10.1109/led.2019.2953088

Cited by 23 publications

(13 citation statements)

References 25 publications

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“…[12,13] The electron-hole injection can be balanced by tuning electron injection barrier height between quantum dots (QDs) and the ETL to reduce electron overflow in the device active region at the cost of brightness [14][15][16][17] or introducing high hole mobility organics into the HTL to improve the hole transport. [18] Organic dopants, as star-shaped 4,4′,4″tris(N-carbazolyl)-triphenyl-amine(TCTA), [19][20][21] linear 4,4′-bis-(carbazole-9-yl)biphenyl(CBP), [22,23] poly[bis(4-phenyl)(2,4,6trimethylphenyl)amine](PTAA), [24] and 1-bis[4-[N,N-di(4tolyl)amino]phenyl]-cyclohexane(TAPC) [25] molecules have achieved a significantly enhanced light-emission and drove further exploration on the molecular engineering for effective doping strategies.…”

Section: Doi: 101002/marc202200187mentioning

confidence: 99%

Enhancing Hole Transport of Quantum‐Dot Light‐Emitting Diodes by a Cruciform Oligothiophene for Effective p‐Type Doping

Zhang

Ren

Wen

et al. 2022

Macromol. Rapid Commun.

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Effective p-type doping is essential to enhance hole transport and balance electron-hole injection in quantum dot light-emitting diodes (QLEDs). Here, an oligothiophene material is adopted as a p-type dopant in the hole-transport layer, considering its cruciform cross-center structure, precise molecular weight, and high purity. Compared with the dopant-free counterpart, hole transport capability at the optimal doping level exhibits a significant improvement, producing a boosted external quantum efficiency (EQE) and luminance up to 20.8%, 213 439 cd m -2 , respectively, among the highest reported on the red-light emission. The work indicates the potential applications of oligothiophene material in red light-emitting devices. IntroductionQuantum dot light-emitting diodes (QLEDs), with unique physical properties such as tunable emission wavelength, light stability, and high color purity, have gained extensive research interests in the next generation of display and lighting devices in recent years. [1][2][3][4][5][6][7][8] Generally, the QLED device has a hybrid structure consisting of an organic hole-transport layer (HTL) and a metal oxide-based electron-transporting layer (ETL). However, compared with electron mobility (10 cm 2 V -1 s -1 ) in the ETL, the relatively low hole mobility (10 -3 cm 2 V -1 s -1 ) in the organic materials like poly(9,9-dioctylfluorene-co-N-(4-(3methylpropyl))diphenylamine) (TFB) and poly (9-vinylcarbazole)

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Section: Doi: 101002/marc202200187mentioning

confidence: 99%

Enhancing Hole Transport of Quantum‐Dot Light‐Emitting Diodes by a Cruciform Oligothiophene for Effective p‐Type Doping

Zhang

Ren

Wen

et al. 2022

Macromol. Rapid Commun.

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“…This reduced current density at higher T5DP‐2,7 amounts can be ascribed to that the aggregation of T5DP‐2,7 at high proportion causes the poor contact between the HTL and QDs and then results in low efficiency of hole injection. [ 13 ] Additionally, electron‐only device (ITO/ZnO/QDs/ZnO:PVP/Al) was also prepared. The injection capability of the HTL with 20 wt% T5DP‐2,7 is the most comparable to that of ZnO:PVP.…”

Section: Resultsmentioning

confidence: 99%

Constructing Effective Hole Transport Channels in Cross‐Linked Hole Transport Layer by Stacking Discotic Molecules for High Performance Deep Blue QLEDs

Zhang

et al. 2022

Advanced Science

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The inadequate hole injection limits the efficiency and lifetime of the blue quantum dot light‐emitting diodes (QLEDs), which severely hampers their commercial applications. Here a new discotic molecule of 3,6,10,11‐tetrakis(pentyloxy)triphenylene‐2,7‐diyl bis(2,2‐dimethylpropanoate) (T5DP‐2,7) is introduced, in which the hole transport channels with superior hole mobility (2.6 × 10 –2 cm 2 V –1 s –1 ) is formed by stacking. The composite hole transport material (HTM) is prepared by blending T5DP‐2,7 with the cross‐linked 4,4′‐ bis(3‐vinyl‐9H‐carbazol‐9‐yl)‐1,1′biphenyl (CBP‐V) which shows the deep highest occupied molecular orbital energy level. The increased hole mobility of the target composite HTM from 10 –4 to 10 –3 cm 2 V –1 s –1 as well as the stepwise energy levels facilitates the hole transport, which would be beneficial for more balanced carrier injection. This composite hole transport layer (HTL) has improved the deep‐blue‐emission performances of Commission International de I'Eclairage of (0.14, 0.04), luminance of 44080 cd m −2 , and external quantum efficiency of 18.59%. Furthermore, when L 0 is 100 cd m −2 , the device lifetime T 50 is extended from 139 to 502 h. The state‐of‐the‐art performance shows the successful promotion of the high‐efficiency for deep blue QLEDs, and indicates that the optimizing HTL by discotic molecule stacking can serve as an excellent alternative for the development of HTL in the future.

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“…Then, the hole injection layer of PEDOT:PSS, the hole transport layer of PVK, the emissive layer of CdSe/ZnS QDs, and the electron injection/transport layer of ZnO were deposited successively by spin coating. The specific parameters of the spin coating and annealing for the functional layers were adopted according to the previously reported procedures. − Finally, the deposition of the Al electrode was completed in a high-vacuum chamber (<10 –4 Pa), resulting in the active area of 3 mm × 3 mm through a shadow mask. The QLEDs were encapsulated by flexible PLE or conventional glass encapsulation inside the glove box, with oxygen and moisture levels of <0.1 ppm, after they were taken out from the thermal evaporation chamber.…”

Section: Methodsmentioning

confidence: 99%

Universal Flexible Lamination Encapsulation Strategy toward Underwater-Operation Electroluminescence Devices

Chen

et al. 2022

ACS Appl. Mater. Interfaces

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A reliable encapsulation technology with scalability and flexibility is urgently needed for electroluminescence devices. Here, we developed a simple, robust, low-cost, and scalable flexible lamination encapsulation strategy with quantum-dot light-emitting diodes (QLEDs) as the model devices. Multilayered Parafilm combining with calcium oxide buffer was used for the lamination encapsulation. We successfully demonstrated that such a Parafilm Lami encapsulation (PLE) not only allowed excellent protection for QLEDs in air but endowed QLED outstanding waterproof performance. As a result, highly efficient and stable flexible waterproof QLEDs were realized based on this PLE, exhibiting maximum external quantum efficiency of ∼8% and long half-luminescence lifetime of over 1.5 h in water. We believe that there are not any obstacles to extending this encapsulation technology to other flexible flat-panel devices, such as organic/perovskite light-emitting diodes.

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Composite Hole Transport Layer Consisting of High-Mobility Polymer and Small Molecule With Deep-Lying HOMO Level for Efficient Quantum Dot Light-Emitting Diodes

Cited by 23 publications

References 25 publications

Enhancing Hole Transport of Quantum‐Dot Light‐Emitting Diodes by a Cruciform Oligothiophene for Effective p‐Type Doping

Enhancing Hole Transport of Quantum‐Dot Light‐Emitting Diodes by a Cruciform Oligothiophene for Effective p‐Type Doping

Constructing Effective Hole Transport Channels in Cross‐Linked Hole Transport Layer by Stacking Discotic Molecules for High Performance Deep Blue QLEDs

Universal Flexible Lamination Encapsulation Strategy toward Underwater-Operation Electroluminescence Devices

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