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Mechanism Research and Device Optimi...

Zhang, Tianqi,

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Mechanism Research and Device Optimization for High Efficiency and High Stability Green InP QLEDs /

Record Type:	Electronic resources : Monograph/item
Title/Author:	Mechanism Research and Device Optimization for High Efficiency and High Stability Green InP QLEDs // Tianqi Zhang.
Author:	Zhang, Tianqi,
Description:	1 electronic resource (206 pages)
Notes:	Source: Dissertations Abstracts International, Volume: 85-04, Section: B.
Contained By:	Dissertations Abstracts International85-04B.
Subject:	Applied physics. -
Online resource:	https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=30640547
ISBN:	9798380412841

Mechanism Research and Device Optimization for High Efficiency and High Stability Green InP QLEDs /
Zhang, Tianqi,

Mechanism Research and Device Optimization for High Efficiency and High Stability Green InP QLEDs /Tianqi Zhang. - 1 electronic resource (206 pages)

Source: Dissertations Abstracts International, Volume: 85-04, Section: B.

Colloidal semiconductor quantum dots (QDs), as new-generation emissive materials, have shown great potential in many device applications, including light-emitting diodes (LEDs), bioimaging, solar cells, and photocatalysis, owing to their quantum size effects, unique physical and optical properties, such as good monochromaticity, convenient band gap tunability, high stability and photoluminescence (PL) quantum yield (QY). Indium phosphide (InP) QDs material is a promising cadmium-free candidate for constructing high-performance QD light-emitting diodes (QLEDs) as the emissive layer. Continuous efforts have been afforded to this topic in recent years. However, the performance of green InP QLEDs is still below the commercialization standard. High efficiency and high stability are two key factors in realizing the application of high-performance QLED devices. In order to achieve a good external quantum efficiency (EQE) and extend the operating lifetime of green InP QLEDs, this thesis has focused on the above two factors to carry out research on the working and degradation mechanisms of green InP QLEDs and has made the following innovative achievements. In the case of low efficiency caused by unbalanced carrier injection, an innovative design of enhanced hole injection based on the electric dipole layer to enhance the hole injection is proposed. A strong forward built-in electric field significantly helps the hole hopping at the interface between the hole injection layer (HIL) and the hole transport layer (HTL). For green InP QLEDs with strong electron injection, this method avoids the confinement of electron injection, thus obtaining a higher radiation recombination rate. Based on this research, the EQE of the optimized device has increased from 4.25% to 7.94%. In addition, the maximum luminance of the green InP QLEDs reaches 52,730 cd·m-2 , which is highest among counterparts.In order to further enhance the efficiency, an electron leakage mechanism in green InP QLEDs is revealed and in-depth studied. Furthermore, an effective approach is proposed to avoid electron leakage by LiF that reduces the Fermi energy difference between green InP QDs and ITO anode. The LiF modification not only suppresses the leaked electrons but also further strengthens the hole injection through a tunneling effect. Based on this approach, an optimized device has achieved a more balanced carrier injection in its emitting layer, resulting in a further enhanced EQE as high as 9.14%. In the case of poor device stability, the degradation mechanism of QLEDs is preliminarily revealed and studied. The dark spots in light distribution imaging and hot spots in thermal imaging of QLEDs are analyzed from the aspects of optics, electricity, and heat. As a result, a coupling degradation mechanism of film formation, current density, and temperature on QLEDs is obtained. In addition, the influence of various factors on the working temperature of QLEDs is systematically researched. Besides improving the operating level in device fabrication, an effective thermal management method is applied to the green InP QLEDs. The optimized device achieved an operating lifetime of T50 100nit = 8,311 hours, which is also a record of green InP QLEDs.In this thesis, the working mechanism and degradation mechanism in green InP QLEDs have been deeply studied. Based on these mechanisms, several approaches are proposed to achieve better carrier balance and lower working temperature. The optimized green InP QLEDs exhibit higher efficiency and higher stability, making them more desirable in display applications. The mechanisms and solutions proposed in the thesis will also provide more ideas for the related fields.

English

ISBN: 9798380412841Subjects--Topical Terms:

3343996
Applied physics.
Subjects--Index Terms:

Carrier injection

Mechanism Research and Device Optimization for High Efficiency and High Stability Green InP QLEDs /
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245 1 0 $a Mechanism Research and Device Optimization for High Efficiency and High Stability Green InP QLEDs / $c Tianqi Zhang.
264 1 $a Ann Arbor : $b ProQuest Dissertations & Theses, $c 2022
300 $a 1 electronic resource (206 pages)
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500 $a Source: Dissertations Abstracts International, Volume: 85-04, Section: B.
500 $a Advisors: Xing, Guichuan; Wang, Kai.
502 $b Ph.D. $c University of Macau $d 2022.
520 $a Colloidal semiconductor quantum dots (QDs), as new-generation emissive materials, have shown great potential in many device applications, including light-emitting diodes (LEDs), bioimaging, solar cells, and photocatalysis, owing to their quantum size effects, unique physical and optical properties, such as good monochromaticity, convenient band gap tunability, high stability and photoluminescence (PL) quantum yield (QY). Indium phosphide (InP) QDs material is a promising cadmium-free candidate for constructing high-performance QD light-emitting diodes (QLEDs) as the emissive layer. Continuous efforts have been afforded to this topic in recent years. However, the performance of green InP QLEDs is still below the commercialization standard. High efficiency and high stability are two key factors in realizing the application of high-performance QLED devices. In order to achieve a good external quantum efficiency (EQE) and extend the operating lifetime of green InP QLEDs, this thesis has focused on the above two factors to carry out research on the working and degradation mechanisms of green InP QLEDs and has made the following innovative achievements. In the case of low efficiency caused by unbalanced carrier injection, an innovative design of enhanced hole injection based on the electric dipole layer to enhance the hole injection is proposed. A strong forward built-in electric field significantly helps the hole hopping at the interface between the hole injection layer (HIL) and the hole transport layer (HTL). For green InP QLEDs with strong electron injection, this method avoids the confinement of electron injection, thus obtaining a higher radiation recombination rate. Based on this research, the EQE of the optimized device has increased from 4.25% to 7.94%. In addition, the maximum luminance of the green InP QLEDs reaches 52,730 cd·m-2 , which is highest among counterparts.In order to further enhance the efficiency, an electron leakage mechanism in green InP QLEDs is revealed and in-depth studied. Furthermore, an effective approach is proposed to avoid electron leakage by LiF that reduces the Fermi energy difference between green InP QDs and ITO anode. The LiF modification not only suppresses the leaked electrons but also further strengthens the hole injection through a tunneling effect. Based on this approach, an optimized device has achieved a more balanced carrier injection in its emitting layer, resulting in a further enhanced EQE as high as 9.14%. In the case of poor device stability, the degradation mechanism of QLEDs is preliminarily revealed and studied. The dark spots in light distribution imaging and hot spots in thermal imaging of QLEDs are analyzed from the aspects of optics, electricity, and heat. As a result, a coupling degradation mechanism of film formation, current density, and temperature on QLEDs is obtained. In addition, the influence of various factors on the working temperature of QLEDs is systematically researched. Besides improving the operating level in device fabrication, an effective thermal management method is applied to the green InP QLEDs. The optimized device achieved an operating lifetime of T50 100nit = 8,311 hours, which is also a record of green InP QLEDs.In this thesis, the working mechanism and degradation mechanism in green InP QLEDs have been deeply studied. Based on these mechanisms, several approaches are proposed to achieve better carrier balance and lower working temperature. The optimized green InP QLEDs exhibit higher efficiency and higher stability, making them more desirable in display applications. The mechanisms and solutions proposed in the thesis will also provide more ideas for the related fields.
546 $a English
590 $a School code: 1382
650 4 $a Applied physics. $3 3343996
650 4 $a Materials science. $3 543314
650 4 $a Computational physics. $3 3343998
650 4 $a Condensed matter physics. $3 3173567
653 $a Carrier injection
653 $a Indium phosphide
653 $a Multi-physics simulation
653 $a Thermal management
653 $a Quantum dots
690 $a 0215
690 $a 0794
690 $a 0611
690 $a 0216
710 2 $a University of Macau. $b Applied Physics and Materials Engineering. $e degree granting institution. $3 3765741
720 1 $a Xing, Guichuan $e degree supervisor.
720 1 $a Wang, Kai $e degree supervisor.
773 0 $t Dissertations Abstracts International $g 85-04B.
790 $a 1382
791 $a Ph.D.
792 $a 2022
856 4 0 $u https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=30640547