Thermal Management Enables Bright and Stable Perovskite Light‐Emitting Diodes

Zhao, Lianfeng; Roh, Kwangdong; Kacmoli, Sara; Kurdi, Khaled Al; Jhulki, Samik; Barlow, Stephen; Marder, Seth R.; Gmachl, Claire F.; Rand, Barry P.

doi:10.1002/adma.202000752

Cited by 162 publications

(208 citation statements)

References 30 publications

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“…27c, d ). The short operational lifetime could be a result of Joule heating and ion-migration induced material and/or interfacial degradation under the bias 9 , 28 , as well as Al diffusion and relevant redox reaction between Pb 2+ and Al 0 47 . An EQE histogram for 40 devices shows an average peak EQE of 9.3% with a low standard deviation of 0.67%, indicating high reproducibility of the VAC-treatment.…”

Section: Resultsmentioning

confidence: 99%

Mixed halide perovskites for spectrally stable and high-efficiency blue light-emitting diodes

et al. 2021

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Bright and efficient blue emission is key to further development of metal halide perovskite light-emitting diodes. Although modifying bromide/chloride composition is straightforward to achieve blue emission, practical implementation of this strategy has been challenging due to poor colour stability and severe photoluminescence quenching. Both detrimental effects become increasingly prominent in perovskites with the high chloride content needed to produce blue emission. Here, we solve these critical challenges in mixed halide perovskites and demonstrate spectrally stable blue perovskite light-emitting diodes over a wide range of emission wavelengths from 490 to 451 nanometres. The emission colour is directly tuned by modifying the halide composition. Particularly, our blue and deep-blue light-emitting diodes based on three-dimensional perovskites show high EQE values of 11.0% and 5.5% with emission peaks at 477 and 467 nm, respectively. These achievements are enabled by a vapour-assisted crystallization technique, which largely mitigates local compositional heterogeneity and ion migration.

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Section: Resultsmentioning

confidence: 99%

Mixed halide perovskites for spectrally stable and high-efficiency blue light-emitting diodes

et al. 2021

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“…Joule heating has been shown to be a critical contributor to EL intensity decay and EQE rolloff at high current densities in PeLEDs. [22][23][24] For our devices, this can be demonstrated by biasing the PeLED at constant current densities and extracting the junction temperature from the high energy tail of the EL spectrum according to the generalized Planck's equation. This has been shown to be an accurate and reliable method to estimate the junction temperature of PeLEDs.…”

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confidence: 99%

Perovskite Light Emitting Diode Characteristics: The Effects of Electroluminescence Transient and Hysteresis

Elkhouly

Gehlhaar

Genoe

et al. 2020

Advanced Optical Materials

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However, due to the transient effects that are, to a large extent, a result of the ionic nature of perovskite materials, the characterization of perovskite optoelectronic devices is often sensitive to the applied measurement protocols. [11,12] This makes it difficult to compare and reproduce the reported device characteristics from different research groups, especially when the protocols are not well described. In the case of perovskite solar cells, it has been shown that the anomalous hysteresis effect, which is highly dependent on the voltage scan rate, range, direction, as well as the device structure, could significantly influence current density-voltage (J-V) characteristics and the reported power conversion efficiency (PCE) value. [13] This has triggered intensive studies on the origin of the device hysteresis and wide discussions on how to report the perovskite solar cell characteristics, leading to clear standards that are broadly followed by the perovskite photovoltaic field. [14] However, much less attention was given to the sensitivity of PeLED characteristics to their measurement protocols, which urged a discussion about the standardization of measurement procedures, and about the best practices for characterization. [15] For PeLEDs, the current density-voltage-radiance/luminance (J-V-R/L), and the EQE-J characteristics are the main figures of merit. Although the hysteresis in J-V characteristics is to date well-understood and attributed to ion migration and interfacial charge trapping, [16-18] the influence of these transient effects and device hysteresis on the PeLED performances lacks investigation. Zhao et al. have shown that under electrical stress, PeLEDs showed an EQE enhancement accompanied by a reduction in the diode ideality factor. [19] This phenomenon was attributed to trap filling by excess ions which reduces nonradiative recombination. It can be observed in many PeLEDs in literature during lifetime measurements, with the stressing time spanning a wide range of timescales from few minutes to several hours. [8,20,21] In this report, we show that the electroluminescence (EL) intensity of PeLEDs changes significantly even on a timescale from 100 ms to a few seconds. Such reversible EL transients, together with the possible device degradation during measurement, could lead to severe device hysteresis, making the reported J-V-R/L and EQE-J curves highly dependent on measurement protocols. Moreover, we show that a method based on pulsed excitation with cooldown time in-between The reproducibility of results is one of the cornerstones of scientific research. However, in emerging technologies, the reported results often tend to be sensitive to the chosen measurement protocol. This can stem from measurement artifacts or from unknown complex underlying phenomena. Metal halide perovskites have emerged as an exciting material system for optoelectronic devices. The anomalous hysteresis in the current density-voltage (J-V) characteristics of perovskite solar cells has triggered wide discussions on how ...

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“…The results suggest beneficial roles of the short NA ligands on improving the device operational stability, possibly originated from the enhanced charge injection which would suppress the Joule heating in the devices during the LED operation. [ 32 ] Further benefiting from the higher PLQY, we achieve a superior EQE of 8.44% and maximum luminance of 31 759 cd cm −2 for optimized devices based on Pb(NA) 2 ‐DDDAm NCs (see Figure 4e,f; Figure S12, Supporting Information). As shown in the Table S1 of the Supporting Information, in comparison to devices based on CsPbBr 3 synthesized from conventional hot‐injection methods, the device performance in the present work demonstrates a comparable peak EQE while a twofold increase in the maximum luminance, suggesting great potential of the synthesis route here.…”

Section: Resultsmentioning

confidence: 98%

Efficient and High‐Luminance Perovskite Light‐Emitting Diodes Based on CsPbBr₃ Nanocrystals Synthesized from a Dual‐Purpose Organic Lead Source

Zhao

Wei

et al. 2020

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Rational engineering of the surface properties of perovskite nanocrystals (PeNCs) is critical to obtain light emitters with simultaneous high photoluminescence efficiency and excellent charge transport properties for light‐emitting diodes (LEDs). However, the commonly used lead halide sources make it hard to rationally optimize the surface compositions of the PeNCs. In addition, previously developed ligand engineering strategies for conventional inorganic nanocrystals easily deteriorate surface properties of the PeNCs, bringing additional difficulties in optimizing their optoelectronic properties. In this work, a novel strategy of employing a dual‐purpose organic lead source for the synthesis of highly luminescent PeNCs with enhanced charge transport property is developed. Lead naphthenate (Pb(NA)2), of which the metal ions work as lead sources while the naphthenate can function as the surface ligands afterward, is explored and the obtained products under different synthesis conditions are comprehensively investigated. Monodispersed cesium lead bromide (CsPbBr3) with controllable size and excellent optical properties, showing superior photoluminescence quantum yields up to 80%, is obtained. Based on the simultaneously enhanced electrical properties of the Pb(NA)2‐derived PeNCs, the resultant LEDs demonstrate a high peak external quantum efficiency of 8.44% and a superior maximum luminance of 31 759 cd cm−2.

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Thermal Management Enables Bright and Stable Perovskite Light‐Emitting Diodes

Cited by 162 publications

References 30 publications

Mixed halide perovskites for spectrally stable and high-efficiency blue light-emitting diodes

Mixed halide perovskites for spectrally stable and high-efficiency blue light-emitting diodes

Perovskite Light Emitting Diode Characteristics: The Effects of Electroluminescence Transient and Hysteresis

Efficient and High‐Luminance Perovskite Light‐Emitting Diodes Based on CsPbBr₃ Nanocrystals Synthesized from a Dual‐Purpose Organic Lead Source

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Thermal Management Enables Bright and Stable Perovskite Light‐Emitting Diodes

Cited by 162 publications

References 30 publications

Mixed halide perovskites for spectrally stable and high-efficiency blue light-emitting diodes

Mixed halide perovskites for spectrally stable and high-efficiency blue light-emitting diodes

Perovskite Light Emitting Diode Characteristics: The Effects of Electroluminescence Transient and Hysteresis

Efficient and High‐Luminance Perovskite Light‐Emitting Diodes Based on CsPbBr3 Nanocrystals Synthesized from a Dual‐Purpose Organic Lead Source

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Efficient and High‐Luminance Perovskite Light‐Emitting Diodes Based on CsPbBr₃ Nanocrystals Synthesized from a Dual‐Purpose Organic Lead Source