Solution-processed, high-performance light-emitting diodes based on quantum dots

Dai, Xingliang; Zhang, Zhenxing; Jin, Yizheng; Niu, Yuan; Cao, Hujia; Liang, Xiaohui; Chen, Liwei; Wang, Jianpu; Peng, Xiaogang

doi:10.1038/nature13829

Cited by 2,312 publications

(2,217 citation statements)

References 33 publications

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“…All perovskite LED device characterizations were carried out at room temperature in a nitrogen-filled glovebox. A Keithley 2400 source meter and a fiber integration sphere (FOIS-1) couple with a QE65 Pro spectrometer was used for the measurements 28 . The LED devices are tested on top of the integration sphere and only forward light emission can be collected, which is consistent with the standard OLED characterization method 29 .…”

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confidence: 99%

Perovskite light-emitting diodes based on solution-processed self-organized multiple quantum wells

et al. 2016

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Perovskite light-emitting diodes based on solution-processed self-organized multiple quantum wells, Nature Photonics, 2016. 10(11) Encouraging performance metrics of light-emitting diodes (LEDs) based on 3Dperovskites, such as low turn-on voltages and external quantum efficiencies (EQEs) of up to 3.5% at high current densities, have been demonstrated 9 . However, the EL quantum efficiency is far behind the limit predicated by ~70% PLQE of the 3D perovskites, mainly due to the existence of current losses caused by incomplete surface coverage of the perovskite films and the fact that the high PLQE can only be obtained at high excitations 8,9 . By using thick (>300 nm) perovskite films, Cho et al.obtained LEDs with over 8% EQE 10 . However, for this device, the turn-on voltage is high and the power efficiency is low, which may result from the thick perovskite layer used. In order to further enhance the performance of 3D perovskite-based LEDs, it is 3 essential to obtain perovskite thin films with both complete surface coverage and high PLQE [8][9][10] . Moreover, device stability, which was proven to be a vital issue in organic-inorganic halide perovskite-based photovoltaics 11 , has not been addressed in perovskite LEDs.The 3D perovskites are actually an extreme case of layered organometal halide perovskites with a general formula of L2(SMX3)n-1MX4, where M, X, L, and S are a divalent metal cation, a halide, and organic cations with long and short chains, respectively ( Fig. 1a) [12][13][14] . Here n is the number of semiconducting MX4 monolayer sheets within the two organic insulating layers (cation L), with n=∞ corresponding to the structure of a 3D perovskite SMX3. With smaller numbers of MX4 layers, quantum confinement effects, such as an increase in bandgap and exciton energy, become important 6,15 . In consequence, the layered perovskites naturally form quantum-well structures. At the opposite extreme, when n=1, the layered perovskites form a monolayer structure of a two-dimensional (2D) perovskite L2MX4. The 2D L2MX4 perovskites generally have good film-formation properties 13 . Nevertheless, the PLQEs of the 2D perovskites are rather low at room temperature, owing to fast exciton quenching rates 6,7 . LEDs based on the 2D perovskites have been attempted, while the devices are either very low in efficiency or only operational at cryogenic temperatures [16][17][18] . Here we demonstrate very efficient (up to 11.7% EQE) and high-brightness EL achievable at room temperature by using solution-processed perovskite multiple quantum wells (MQWs) with an energy cascade, which can combine the advantages of 2D and 3D perovskites. We note, a relevant perovskite LED work 19 which shows a peak EQE of 8.8% has been published online during the revision of this paper.A precursor solution of 1-naphthylmethylamine iodide (NMAI), formamidinium iodide (FAI), and PbI2 with a molar ratio of 2:1:2 dissolved in N,N-dimethylformamide (DMF) was used to deposit perovskite films (see Methods for details), which are abbreviated as NFPI...

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Perovskite light-emitting diodes based on solution-processed self-organized multiple quantum wells

et al. 2016

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“…Electroluminescent devices based on QDs (QLEDs) and metal halide perovskites have emerged with sky-rocketing device parameters that outperform OLED in many aspects. [125][126][127] Compared to OLED and QLED, PeLEDs possess advantages in terms of narrower FWHM thus potentially higher color gamut in display application, high external quantum efficiency especially for the green emission devices, and the possibility of in situ fabrication that provides an efficient and convenient way for scalable production.…”

Section: Electroluminescencementioning

confidence: 99%

In Situ Fabricated Perovskite Nanocrystals: A Revolution in Optical Materials

Chang

Bai

Zhong

2018

Advanced Optical Materials

192

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in bulk halide perovskites, long carrier diffusion length, and an absorption range covering the visible solar spectrum, collectively enable the high performance of photo electricity conversion. Compared to the bulk materials, perovskite nanocrystals or quantum dots (usually denoted as PNCs or PQDs) show obvious excitonic features with enhanced photoluminescence (PL) properties due to the well-known size-dependent quantum confinement effects. [14][15][16][17] The combination of color saturated emissions, super high quantum yield (QY), as well as easy processing inspired the intensive exploration of PNCs as light emitters, which is now under spotlights in the field of optical materials.The first perspective aim of PNCs is to alternate the state-of-the-art CdSe or InP quantum dots (QDs) as new generation luminescence materials. [18,19] As shown in Figure 1, these QD materials have been well demonstrated to be potential functional components for photonic and optoelectronic applications, and are currently on the way to industrialization. [20][21][22][23] Specifically, QDs can be employed as fluorescence labels, [24] laser gain media, [25] LED phosphors, [26] and down-shifting films for LCD backlights. [27,28] They can also be processed into thin film for optoelectronic devices including solar cells, [29] photodetectors, [30,31] transistors [32] and LEDs. [33] The PNCs outcompete these conventional QDs in terms of narrower full width at half maximum (FWHM) and low fabrication cost, but most importantly, the ease of in situ preparation. [34,35] Herein, this progress report highlight the developments of in situ fabricated PNCs.Colloidal semiconductor QDs are typically synthesized ex situ in flasks by hot injection method, stabilized by surface ligands. [36][37][38][39] To incorporate such solution based materials into applications usually requires purification, redispersion and surface engineering. For instance, ligand exchange is often employed to disperse QDs into aimed solvent, inducing defects that inevitably derogating the PLQYs. [40] Moreover, the organic ligands themselves also suffer from the risk of disabsorbing, reducing the stability of the QDs and thus the final devices. [41] Because halide perovskite are ionic compounds that can be well dissolved into polar solvents, PNCs can be fabricated through either ex situ routes in flask or in situ strategies on substrates. The in situ fabricated PNCs are adaptable to devices integration due to their scalable and low-cost manufacturing. In this regard, more and more efforts have been made in terms of the controlling synthesis, physical properties and device applications of PNC materials.After over 30 years of development, colloidal quantum dots have now become mature luminescent materials in photonic and optoelectronic operations and start to hit the market. The emerging perovskite nanocrystals are expected to promote large-scale commercialization due to their superior optical properties as well as low cost and easy fabrication. This progress report is focused on the...

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“…Recently these QLEDs were presented with highly promising performances for device application including luminance levels above 200.000 cd/m 2 and efficiencies greater than 18%. 8,9,35 In the case of iTMCLECs, as discussed above, the variation of emission color turned out to be challenging, so that the use of QDs could fulfill that need. The incorporation of QDs in p-LECs is rarely studied yet, 36 while the implementation of QDs in iTMC-LECs was not reported so far.…”

Section: ■ Introductionmentioning

confidence: 99%

Quantum Dot/Light-Emitting Electrochemical Cell Hybrid Device and Mechanism of Its Operation

Frohleiks

Wepfer

Keleştemur

et al. 2016

ACS Appl. Mater. Interfaces

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A new type of light-emitting hybrid device based on colloidal quantum dots (QDs) and an ionic transition metal complex (iTMC) light-emitting electrochemical cell (LEC) is introduced. The developed hybrid devices show light emission from both active layers, which are combined in a stacked geometry. Time-resolved photoluminescence experiments indicate that the emission is controlled by direct charge injection into both the iTMC and the QD layer. The turn-on time (time to reach 1 cd/m 2 ) at constant voltage operation is significantly reduced from 8 min in the case of the reference LEC down to subsecond in the case of the hybrid device. Furthermore, luminance and efficiency of the hybrid device are enhanced compared to reference LEC directly after device turn-on by a factor of 400 and 650, respectively. We attribute these improvements to an increased electron injection efficiency into the iTMC directly after device turn-on.

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Solution-processed, high-performance light-emitting diodes based on quantum dots

Cited by 2,312 publications

References 33 publications

Perovskite light-emitting diodes based on solution-processed self-organized multiple quantum wells

Perovskite light-emitting diodes based on solution-processed self-organized multiple quantum wells

In Situ Fabricated Perovskite Nanocrystals: A Revolution in Optical Materials

Quantum Dot/Light-Emitting Electrochemical Cell Hybrid Device and Mechanism of Its Operation

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