Nonlinear electro-thermal modeling and field-simulation of OLEDs for lighting applications I: Algorithmic fundamentals

Pohl, László; Kollar, E.; Poppe, A.; Kohári, Zsolt

doi:10.1016/j.mejo.2011.06.011

Cited by 24 publications

(9 citation statements)

References 8 publications

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“…Another approach is to accept the self‐heating with the benefit that higher currents are driven, allowing to reach higher light output. Several publications show simulations of self‐heating in OLEDs, and some of them consider electrothermal modeling, demonstrating that self‐heating causes brightness inhomogeneities, but the results do not describe the entire behavior as we will show in this work. To understand the prospects and limitations of self‐heating, a description of the OLED at strong self‐heating is required.…”

Section: Introductionmentioning

confidence: 72%

Feel the Heat: Nonlinear Electrothermal Feedback in Organic LEDs

Fischer

Koprucki

Gärtner

et al. 2014

Adv Funct Materials

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For lighting applications, organic light-emitting diodes (OLED) need much higher brightness than for displays, leading to self-heating. Due to the temperature-activated transport in organic semiconductors, this can result in brightness inhomogeneities and catastrophic failure. Here, it is shown that due to the strong electrothermal feedback of OLEDs, the common spatial current and voltage distribution is completely changed, requiring advanced device modeling and operation concepts. This study clearly demonstrates the effect of S-shaped negative differential resistance in OLEDs induced by self-heating. As a consequence, for increasing voltage, regions with declining voltages are propagating through the device, and even more interestingly, a part of these regions show even decreasing currents, leading to strong local variation in luminance. The expected breakthrough of OLED lighting technology will require an improved price performance ratio, and the realization of modules with very high brightness but untainted appearance is considered to be an essential step into this direction. Thus, a deeper understanding of the control of electrothermal feedback will help to make OLEDs in lighting more competitive.

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Section: Introductionmentioning

confidence: 72%

Feel the Heat: Nonlinear Electrothermal Feedback in Organic LEDs

Fischer

Koprucki

Gärtner

et al. 2014

Adv Funct Materials

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“…The approach of overall modeling of a CoB device described in the present study was inspired by our previous work that targeted multi-domain simulation of large-area OLEDs [34,35]. For OLED simulations the FVM was applied to get a 3D network of multi-domain elementary cells.…”

Section: Detailed 3d Phosphor Model With a Numerical Approachmentioning

confidence: 99%

“…In the case of phosphor-converted white CoB LEDs, however, the first approach of using compact models only cannot be applied because of the distributed, multi-domain nature of the phosphor layer, involving: Regarding the description of the multi-domain behavior of the blue LED chips, we relied on one of the Spice-like multi-domain LED models we developed earlier [28]. The heat transfer within the bulk of the LED chips, the ceramics substrate and within the phosphor layer is treated by BME's proprietary conduction-mode only thermal field solver [32,33] that has already been successfully adapted to the multi-domain modeling of large-area OLED devices [34,35].…”

mentioning

confidence: 99%

Mixed Detailed and Compact Multi-Domain Modeling to Describe CoB LEDs

et al. 2020

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Large area multi-chip LED devices, such as chip-on-board (CoB) LEDs, require the combined use of chip-level multi-domain compact LED models (Spice-like compact models) and the proper description of distributed nature of the thermal environment (the CoB substrate and phosphor) of the LED chips. In this paper, we describe such a new numerical solver that was specifically developed for this purpose. For chip-level, the multi-domain compact modeling approach of the Delphi4LED project is used. This chip-level model is coupled to a finite difference scheme based numerical solver that is used to simulate the thermal phenomena in the substrate and in the phosphor (heat transfer and heat generation). Besides solving the 3D heat-conduction problem, this new numerical simulator also tracks the propagation and absorption of the blue light emitted by the LED chips, as well as the propagation and absorption of the longer wavelength light that is converted by the phosphor from blue. Heat generation in the phosphor, due to conversion loss (Stokes shift), is also modeled. To validate our proposed multi-domain model of the phosphor, dedicated phosphor and LED package samples with known resin—phosphor powder ratios and known geometry were created. These samples were partly used to identify the nature of the temperature dependence of phosphor-conversion efficiency and were also used as simple test cases to “calibrate” and test the new numerical solver. With the models developed, combined simulation of the LED chip and the CoB substrate + phosphor for a known CoB LED device is shown, and the simulation results are compared to measurement results.

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“…In the past European project called Fast2Light we worked out a method for multi-domain simulation of large area OLEDs (Pohl, 2012, Kohári, 2013. In case of OLEDs both heat conduction, electrical conduction (through the transparent ITO layer) and light generation (in the LEP layer) were of distributed nature.…”

Section: Thermal Model Of Cree Xp-e2mentioning

confidence: 99%

Multi-Domain Characterization of Cob Leds

Hegedüs

Hantos

Németh

et al. 2019

PROCEEDINGS OF the 29th Quadrennial Session of the CIE

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In a recent European H2020 project on LED characterisation and modelling (Delphi4LED, www.delphi4LED.eu) the major target was to represent physical LED package types by their digital twins in form of multi-domain compact models. In this project a specific task was devoted to CoB LEDs. Phosphor converted white CoB LEDs are large area devices on a ceramic substrate of high thermal conductivity, with a few dozens of LED chips mounted, covered by a phosphor layer. Such devices represent real technical challenges both in terms of their physical measurement and modelling. In this paper we report on our work regarding measurement and modelling of such devices performed in the context of the aforementioned project.

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Nonlinear electro-thermal modeling and field-simulation of OLEDs for lighting applications I: Algorithmic fundamentals

Cited by 24 publications

References 8 publications

Feel the Heat: Nonlinear Electrothermal Feedback in Organic LEDs

Feel the Heat: Nonlinear Electrothermal Feedback in Organic LEDs

Mixed Detailed and Compact Multi-Domain Modeling to Describe CoB LEDs

Multi-Domain Characterization of Cob Leds

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