Quantum-dot light-emitting diodes(QLEDs)promise a new generation of low-cost,efficient,bright,and stable light sources.Achieving large-area patterning of high-resolution QLED arrays is essential for display applicatio...Quantum-dot light-emitting diodes(QLEDs)promise a new generation of low-cost,efficient,bright,and stable light sources.Achieving large-area patterning of high-resolution QLED arrays is essential for display applications.However,patterning of micro-QLEDs arrays via conventional photolithography,the most established and scalable technique capable of producing micrometer-scale patterns,poses challenges because the chemicals and solvents used can damage quantum dot emissive layers and charge transport layers(CTLs)during ultraviolet(UV)exposure and development.Here,we address these challenges by designing a novel hole transport layer(HTL),poly((9,9-dioctylfluorenyl-2,7-diyl)-co-(9-(2-ethylhexyl)-carbazole-3,6-diyl)-co-(9-(4-(4-vinylphenoxy)butyl)-carbazole-3,6-diyl))(PF8Cz-X),which replaces reactive triphenylamine(TPA)units with chemically stable carbazole derivatives and introduces vinylphenoxy groups that crosslink upon annealing,enhancing solvent resistance.Utilizing PF8Cz-X,we fabricated efficient and high-resolution micro-QLEDs arrays with pixel sizes down to~2μm,achieving resolutions up to 6000 pixels per inch.The red,green,and blue micro-QLEDs demonstrate peak external quantum efficiencies(EQEs)of 16.5%,20.1%,and 12.7%,respectively,matching those of un-patterned devices.Our work reveals that conventional photolithography can be effectively employed for the fabrication of high-resolution micro-QLEDs array,paving the way towards advanced display applications in augmented reality(AR)and virtual reality(VR)technologies.展开更多
All-solution-processed inverted quantum dot(QD)light-emitting diodes(QLEDs)with transparent bottom cathodes can be directly connected to the n-type thin-film transistors,offering a feasible solution for low-cost activ...All-solution-processed inverted quantum dot(QD)light-emitting diodes(QLEDs)with transparent bottom cathodes can be directly connected to the n-type thin-film transistors,offering a feasible solution for low-cost active matrix-driven QD displays.However,the subsequent solution-deposition of the hole-transporting layer destroys the underneath QD films,resulting in largely deteriorated device performance.Various strategies have been implemented to prevent QD film from dissolution,but all at a heavy cost of device performance suffering from either reduced efficiency or increased driving voltage.Here,a facile and effective water-treatment approach for QD film to fabricate inverted QLEDs through all solution processing is reported.The water treatment substitutes the long-chain oleate ligands with hydroxyl groups,resulting in significantly improved non-polar solvent resistance of the QD films.Importantly,the QD films reserve their excellent photoluminescence efficiency after water treatment.With the water-treated QD film as the emissive layer,all-solution-processed inverted red QLED with a peak external quantum efficiency of 19.6%,a turn-on voltage of 1.8 V,and a T50 operational lifetime of 150,000 h at 100 cd·m^(-2) was achieved.Furthermore,efficient and low-voltage-driven green and blue QLEDs can also be prepared with this method.This work provides a feasible strategy for the fabrication of high-performance all-solution-processed inverted QLEDs,paving the way toward achieving QLEDs by all ink-jet printing.展开更多
Quantum-dot light-emitting diodes(QLEDs)are multilayer electroluminescent devices promising for next-generation display and solid-state-lighting technologies.In the state-of-the-art QLEDs,hole-injection layers(HILs)wi...Quantum-dot light-emitting diodes(QLEDs)are multilayer electroluminescent devices promising for next-generation display and solid-state-lighting technologies.In the state-of-the-art QLEDs,hole-injection layers(HILs)with high work functions are generally used to achieve efficient hole injection.In these devices,Fermi-level pinning,a phenomenon often observed in heterojunctions involving organic semiconductors,can take place in the hole-injection/hole-transporting interfaces.However,an in-depth understanding of the impacts of Fermi-level pinning at the hole-injection/hole-transporting interfaces on the operation and performance of QLEDs is still lacking.Here,we develop a set of NiOx HILs with controlled work functions of 5.2–5.9 eV to investigate QLEDs with Fermi-level pinning at the hole-injection/hole-transporting interfaces.The results show that despite that Fermi-level pinning induces identical apparent hole-injection barriers,the red QLEDs using HILs with higher work functions show improved efficiency roll-off and better operational stability.Remarkably,the devices using the NiOx HILs with a work function of 5.9 eV demonstrate a peak external quantum efficiency of~18.0%and a long T95 operational lifetime of 8,800 h at 1,000 cd·m^(−2),representing the best-performing QLEDs with inorganic HILs.Our work provides a key design principle for future developments of the hole-injection/hole-transporting interfaces of QLEDs.展开更多
基金supported by the National Key Research and Development Program of China(No.2022YFB3606503)the National Natural Science Foundation of China(No.22405233)+1 种基金the China Postdoctoral Science Foundation(No.2023M733019)the Zhejiang Student Technology and Innovation Program(No.2024R401174(X.M.)).
文摘Quantum-dot light-emitting diodes(QLEDs)promise a new generation of low-cost,efficient,bright,and stable light sources.Achieving large-area patterning of high-resolution QLED arrays is essential for display applications.However,patterning of micro-QLEDs arrays via conventional photolithography,the most established and scalable technique capable of producing micrometer-scale patterns,poses challenges because the chemicals and solvents used can damage quantum dot emissive layers and charge transport layers(CTLs)during ultraviolet(UV)exposure and development.Here,we address these challenges by designing a novel hole transport layer(HTL),poly((9,9-dioctylfluorenyl-2,7-diyl)-co-(9-(2-ethylhexyl)-carbazole-3,6-diyl)-co-(9-(4-(4-vinylphenoxy)butyl)-carbazole-3,6-diyl))(PF8Cz-X),which replaces reactive triphenylamine(TPA)units with chemically stable carbazole derivatives and introduces vinylphenoxy groups that crosslink upon annealing,enhancing solvent resistance.Utilizing PF8Cz-X,we fabricated efficient and high-resolution micro-QLEDs arrays with pixel sizes down to~2μm,achieving resolutions up to 6000 pixels per inch.The red,green,and blue micro-QLEDs demonstrate peak external quantum efficiencies(EQEs)of 16.5%,20.1%,and 12.7%,respectively,matching those of un-patterned devices.Our work reveals that conventional photolithography can be effectively employed for the fabrication of high-resolution micro-QLEDs array,paving the way towards advanced display applications in augmented reality(AR)and virtual reality(VR)technologies.
基金This work was financially supported by the National Natural Science Foundation of China(Nos.61905230,52072355,11904345,52103241,and 61904160)Natural Science Foundation of Zhejiang Province(No.LQ19F040004)the Liu Zugang Expert Workstation of Yunnan Province。
文摘All-solution-processed inverted quantum dot(QD)light-emitting diodes(QLEDs)with transparent bottom cathodes can be directly connected to the n-type thin-film transistors,offering a feasible solution for low-cost active matrix-driven QD displays.However,the subsequent solution-deposition of the hole-transporting layer destroys the underneath QD films,resulting in largely deteriorated device performance.Various strategies have been implemented to prevent QD film from dissolution,but all at a heavy cost of device performance suffering from either reduced efficiency or increased driving voltage.Here,a facile and effective water-treatment approach for QD film to fabricate inverted QLEDs through all solution processing is reported.The water treatment substitutes the long-chain oleate ligands with hydroxyl groups,resulting in significantly improved non-polar solvent resistance of the QD films.Importantly,the QD films reserve their excellent photoluminescence efficiency after water treatment.With the water-treated QD film as the emissive layer,all-solution-processed inverted red QLED with a peak external quantum efficiency of 19.6%,a turn-on voltage of 1.8 V,and a T50 operational lifetime of 150,000 h at 100 cd·m^(-2) was achieved.Furthermore,efficient and low-voltage-driven green and blue QLEDs can also be prepared with this method.This work provides a feasible strategy for the fabrication of high-performance all-solution-processed inverted QLEDs,paving the way toward achieving QLEDs by all ink-jet printing.
基金the National Natural Science Foundation of China(Nos.91833303,51911530155,91733302,22001187,and 52062019)the Key Research and Development Program of Zhejiang Province(No.2020C01001)the Natural Science Research Foundation of Jiangsu Higher Education Institutions(No.20KJB150032).
文摘Quantum-dot light-emitting diodes(QLEDs)are multilayer electroluminescent devices promising for next-generation display and solid-state-lighting technologies.In the state-of-the-art QLEDs,hole-injection layers(HILs)with high work functions are generally used to achieve efficient hole injection.In these devices,Fermi-level pinning,a phenomenon often observed in heterojunctions involving organic semiconductors,can take place in the hole-injection/hole-transporting interfaces.However,an in-depth understanding of the impacts of Fermi-level pinning at the hole-injection/hole-transporting interfaces on the operation and performance of QLEDs is still lacking.Here,we develop a set of NiOx HILs with controlled work functions of 5.2–5.9 eV to investigate QLEDs with Fermi-level pinning at the hole-injection/hole-transporting interfaces.The results show that despite that Fermi-level pinning induces identical apparent hole-injection barriers,the red QLEDs using HILs with higher work functions show improved efficiency roll-off and better operational stability.Remarkably,the devices using the NiOx HILs with a work function of 5.9 eV demonstrate a peak external quantum efficiency of~18.0%and a long T95 operational lifetime of 8,800 h at 1,000 cd·m^(−2),representing the best-performing QLEDs with inorganic HILs.Our work provides a key design principle for future developments of the hole-injection/hole-transporting interfaces of QLEDs.
