Promotion of hole injection enabled by GaInN/GaN light-emitting triodes and its effect on the efficiency droop

The efficiency droop in GaInN/GaN blue light-emitting diodes (LEDs) usually commences at current density around 10 A/cm2 and the efficiency decreases monotonically after the droop onset. GaN-based LEDs suffer seriously, at typical operating current densities (10–100 A/cm2), by the efficiency droop. Efficiency re-climbing is observed in the typical droop regime at cryogenic temperatures below 125K. The “efficiency re-climbing” coincides with a distinct increase in device conductivity, which is mainly attributed to an enhancement in p-type conductivity due to field ionization of acceptors. The “efficiency re-climbing” phenomenon implies an approach of solving efficiency droop by enhancing hole injection by external electric field.

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GaN Light-Emitting Triodes (LETs) for High-Efficiency Hole Injection and for Assessment of the Physical Origin of the Efficiency Droop

10.21236/ada471030 ◽

2007 ◽

Author(s):

E. F. Schubert ◽

Jong K. Kim

Keyword(s):

High Efficiency ◽

Efficiency Droop ◽

Hole Injection ◽

Physical Origin ◽

Light Emitting

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EFFICIENCY DROOP IN GaInN HIGH-POWER LIGHT-EMITTING DIODES

International Journal of High Speed Electronics and Systems ◽

10.1142/s0129156411006581 ◽

2011 ◽

Vol 20 (02) ◽

pp. 247-265 ◽

Cited By ~ 3

Author(s):

MARTIN F. SCHUBERT ◽

JONG KYU KIM

Keyword(s):

Active Region ◽

Auger Recombination ◽

Light Emitting Diodes ◽

Internal Quantum Efficiency ◽

Efficiency Droop ◽

Hole Injection ◽

Light Emitting ◽

High Drive ◽

Device Structures ◽

Substantial Effort

GaN -based light-emitting diodes suffer from high-current loss mechanisms that lead to a significant decrease in internal quantum efficiency at high drive currents. This phenomenon, known as "efficiency droop," is a major problem for solid-state lighting applications, in which light-emitting diodes are driven at high currents to deliver large optical powers. Although substantial effort has been invested to uncover the physical origin and mitigate the effects of efficiency droop, there is still a lack of consensus on the dominant mechanism responsible. In this article, we review several mechanisms that have been proposed as explanations of efficiency droop, including junction heating, carrier delocalization, Auger recombination, and electron leakage from the active region. In addition, device structures intended to mitigate the droop-causing mechanism – (i) thick quantum wellsl, (ii) enhanced hole-injection efficiency structures, and (iii) polarization-matched active region – are discussed.

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Efficiency droop due to electron spill-over and limited hole injection in III-nitride visible light-emitting diodes employing lattice-matched InAlN electron blocking layers

Applied Physics Letters ◽

10.1063/1.4759044 ◽

2012 ◽

Vol 101 (16) ◽

pp. 161110 ◽

Cited By ~ 71

Author(s):

Suk Choi ◽

Mi-Hee Ji ◽

Jeomoh Kim ◽

Hee Jin Kim ◽

Md. M. Satter ◽

...

Keyword(s):

Visible Light ◽

Light Emitting Diodes ◽

Efficiency Droop ◽

Hole Injection ◽

Light Emitting ◽

Lattice Matched

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Controlled Injection of Holes into ALQ3 Based Oleds by Means of An Oxidized Transport Layer

MRS Proceedings ◽

10.1557/proc-708-bb3.27 ◽

2001 ◽

Vol 708 ◽

Author(s):

Mathew K. Mathai ◽

Keith A. Higginson ◽

Bing R. Hsieh ◽

Fotios Papadimitrakopoulos

Keyword(s):

Indium Tin Oxide ◽

Oxidative Degradation ◽

Transport Layer ◽

Hole Injection ◽

Carrier Injection ◽

Salt Loading ◽

Light Emitting ◽

Hole Transporting ◽

Intrinsic Degradation ◽

Variable Conductivity

ABSTRACTIn this paper we report a method for tuning the extent of hole injection into the active light emitting tris- (8-hydroxyquinoline) aluminum (Alq3) layer in organic light emitting diodes (OLEDs). This is made possible by modifying the indium tin oxide (ITO) anode with an oxidized transport layer (OTL) comprising a hole transporting polycarbonate of N,N'-bis(3-hydroxymethyl)-N,N'-bis(phenyl) benzidine and diethylene glycol (PC-TPB-DEG) doped with varying concentrations of antimonium hexafluoride salt of N,N,N',N'-tetra-p-tolyl-4,4'-biphenyldiamine (TMTPD+ SbF6-). The conductivity of the OTL can be changed over three orders of magnitude depending on salt loading. The analysis of hole and electron current variations in these devices indicates that optimizing the conductivity of the OTL enables the modulation of hole injection into the Alq3 layer. The bipolar charge transport properties for OLEDs in which the interfacial carrier injection barriers have been minimized, are governed by the conductivities of the respective layers and in this case it is shown that the variable conductivity of the OTL does allow for better control of the same. Accordingly, varying the concentration of holes in the device indicates that beyond an optimum concentration of holes, further hole injection results in the formation of light quenching cationic species and the initiation of oxidative degradation processes in the Alq3 layer, thus accelerating the intrinsic degradation of these devices. The variable conductivity of the OTL can hence be used to minimize the occurrence of these processes.

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The negative effect of toluene on poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) hole injection layer and its role in reducing the stability of solution-coated organic light-emitting devices

Synthetic Metals ◽

10.1016/j.synthmet.2021.116704 ◽

2021 ◽

Vol 273 ◽

pp. 116704

Author(s):

Hyeonghwa Yu ◽

Hany Aziz

Keyword(s):

Hole Injection ◽

Light Emitting ◽

Light Emitting Devices ◽

Hole Injection Layer ◽

Stability Of Solution ◽

Organic Light ◽

Negative Effect ◽

Organic Light Emitting Devices ◽

The Stability

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Large Area Emission in p-Type Polymer-Based Light-Emitting Field-Effect Transistors by Incorporating Charge Injection Interlayers

Materials ◽

10.3390/ma14040901 ◽

2021 ◽

Vol 14 (4) ◽

pp. 901

Author(s):

Gizem Acar ◽

Muhammad Javaid Iqbal ◽

Mujeeb Ullah Chaudhry

Keyword(s):

Field Effect ◽

Field Effect Transistors ◽

Charge Injection ◽

Limiting Factors ◽

Hole Injection ◽

Large Area ◽

Device Structure ◽

Light Emitting ◽

Emission Area ◽

P Type

Organic light-emitting field-effect transistors (LEFETs) provide the possibility of simplifying the display pixilation design as they integrate the drive-transistor and the light emission in a single architecture. However, in p-type LEFETs, simultaneously achieving higher external quantum efficiency (EQE) at higher brightness, larger and stable emission area, and high switching speed are the limiting factors for to realise their applications. Herein, we present a p-type polymer heterostructure-based LEFET architecture with electron and hole injection interlayers to improve the charge injection into the light-emitting layer, which leads to better recombination. This device structure provides access to hole mobility of ~2.1 cm2 V−1 s−1 and EQE of 1.6% at a luminance of 2600 cd m−2. Most importantly, we observed a large area emission under the entire drain electrode, which was spatially stable (emission area is not dependent on the gate voltage and current density). These results show an important advancement in polymer-based LEFET technology toward realizing new digital display applications.

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