Sudden death of organic light-emitting diodes

Rocha, Paulo R. F.; Gomes, Henrique L.; Asadi, Kamal; Katsouras, Ilias; Bory, BF Benjamin; Verbakel, Frank; Weijer, Peter van de; Leeuw, DM Dago de; Meskers, Stefan C. J.

doi:10.1016/j.orgel.2015.02.009

Cited by 10 publications

(5 citation statements)

References 52 publications

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“…2023, 35, 2207993 In spite of this, some works report on the null effect, or even a detrimental impact on the performance upon introducing a LiF interlayer due to charged defects accumulation. [79] Aimed at deconvoluting the influence of the perovskite ions and those of the thermally evaporated ionic interfacial layer, a series of LEDs with increasing LiF content were characterized by IS and LEVS, whose results are presented in Figure 6a,b.…”

Section: Resultsmentioning

confidence: 99%

Radiative Recombination Processes in Halide Perovskites Observed by Light Emission Voltage Modulated Spectroscopy

et al. 2023

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and discharge of the carriers at the contact layers; [12,[25][26][27] however, these phenomena are currently not very well understood.The light emission kinetics in perovskite LEDs and in organic light-emitting diodes (OLEDs) is usually investigated using a range of steady-state and timeresolved methods. [26,28] Remarkably, frequency-resolved methods such as impedance spectroscopy (IS) are highly effective for the separation of concomitant kinetic phenomena. [29] The connection between time transients and light-stimulated frequency methods in halide perovskite has been reviewed recently. [30] Here, we explore a new experimental measuring technique that can provide significant information about recombination in high-performance solar cells and LEDs. We analyze the frequency-resolved light emission with respect to an applied modu lated voltage, that we denote light emission voltage modulated spectroscopy (LEVS). The main point of this investigation is to reveal significant features of the radiative charge recombination that are difficult to be discerned in other measurement techniques. [30] This methodology will be especially useful when the radiative recombination event is convoluted with previous electronic carrier steps such as transport, trapping, or contact polarization effects, and/or ionic-related phenomena. It has previously been remarked that the capacitance and luminance of LEDs show correlated features [21,31,32] and some studies of electrically stimulated light emission spectroscopy have been reported, [33][34][35] but unfortunately, a general methodology has not been fully developed.Here we describe the first LEVS experiments in halide perovskite LEDs and establish an equivalent circuit model to understand the observed spectra, based on the previous experience in IS. We show that the method provides unique information on the recombination processes that cannot be accessed by purely electrical techniques, thus highlighting the interest of this new experimental technique for the characterization of optoelectronic devices, especially those presenting multiple physical phenomena, as it is the case of halide perovskite-based systems. The Transfer Functions of Frequency Resolved Measurements IS is a general-purpose characterization technique that is used in a large variety of fields to extract dynamic information on anyThe kinetics of light emission in halide perovskite light-emitting diodes (LEDs) and solar cells is composed of a radiative recombination of voltage-injected carriers mediated by additional steps such as carrier trapping, redistribution of injected carriers, and photon recycling that affect the observed luminescence decays. These processes are investigated in high-performance halide perovskite LEDs, with external quantum efficiency (EQE) and luminance values higher than 20% and 80 000 Cd m −2 , by measuring the frequency-resolved emitted light with respect to modulated voltage through a new methodology termed light emission voltage modulated spectroscopy (LEVS). The spectra are shown to provid...

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Section: Resultsmentioning

confidence: 99%

Radiative Recombination Processes in Halide Perovskites Observed by Light Emission Voltage Modulated Spectroscopy

et al. 2023

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“…Reversible, electrically induced formation of anion vacancy sites (F-center) in ionic-wide bandgap semiconductors has also been demonstrated for alkali halide-polymer diodes [26][27][28][29].…”

Section: Charge Trapping and Electroformingmentioning

confidence: 99%

Resistive Switching in Metal Oxide/Organic Semiconductor Nonvolatile Memories

Gomes¹,

Leeuw²,

Meskers³

2018

Memristor and Memristive Neural Networks

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Diodes incorporating a bilayer of a metal oxide and an organic semiconductor can show unipolar, nonvolatile memory behavior after electroforming. Electroforming involves dielectric breakdown induced by prolonged bias voltage stress. When the power dissipated during breakdown is limited, electroforming is reversible and involves formation of defects at the organic-oxide interface that can heal spontaneously. When the power dissipation during breakdown exceeds a certain threshold, electroforming becomes irreversible. The fully electroformed diodes show electrical bistability, featuring (meta) stable states with low and high conduction that can be programmed by voltage pulses. The high conduction results from current flowing via filamentary paths. The bistability is explained by the coexistence of two thermodynamically stable phases at the interface between semiconductor and oxide. One phase contains mainly ionized defects and has a low work function, while the other phase has mainly neutral defects and a high work function. In the diodes, domains of the phase with low work function give rise to current filaments. In the filaments, Joule heating will raise temperature locally. When the temperature exceeds the critical temperature, the filament will switch off. The switching involves a collective recombination of charge carriers trapped at the defects as evidenced by bursts of electroluminescence.

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“…[59][60][61] Assuming that in the double layer the charge density is the same as the trap density for the electrons at the polymer interface, 8 Â 10 17 m 2 , we can easily calculate the work function shift DV ¼ rz=e 0 e r with z the distance between the layers of opposite charge and r the (average) 2D charge density. Taking a distance z of about one nanometer, the presence of the double layer will induce a shift of the effective work function of the metal electrode of typically several volts.…”

Section: Relation Of the 2d Ising Predictions With Experimental Mementioning

confidence: 99%

Unipolar resistive switching in metal oxide/organic semiconductor non-volatile memories as a critical phenomenon

Bory

Rocha

Gomes

et al. 2015

Journal of Applied Physics

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Diodes incorporating a bilayer of an organic semiconductor and a wide bandgap metal oxide can show unipolar, non-volatile memory behavior after electroforming. The prolonged bias voltage stress induces defects in the metal oxide with an areal density exceeding 1017 m−2. We explain the electrical bistability by the coexistence of two thermodynamically stable phases at the interface between an organic semiconductor and metal oxide. One phase contains mainly ionized defects and has a low work function, while the other phase has mainly neutral defects and a high work function. In the diodes, domains of the phase with a low work function constitute current filaments. The phase composition and critical temperature are derived from a 2D Ising model as a function of chemical potential. The model predicts filamentary conduction exhibiting a negative differential resistance and nonvolatile memory behavior. The model is expected to be generally applicable to any bilayer system that shows unipolar resistive switching.

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Sudden death of organic light-emitting diodes

Cited by 10 publications

References 52 publications

Radiative Recombination Processes in Halide Perovskites Observed by Light Emission Voltage Modulated Spectroscopy

Radiative Recombination Processes in Halide Perovskites Observed by Light Emission Voltage Modulated Spectroscopy

Resistive Switching in Metal Oxide/Organic Semiconductor Nonvolatile Memories

Unipolar resistive switching in metal oxide/organic semiconductor non-volatile memories as a critical phenomenon

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