Li and Mg Co-Doped Zinc Oxide Electron Transporting Layer for Highly Efficient Quantum Dot Light-Emitting Diodes

Kim, Hyo‐Min; Cho, Sinyoung; Kim, Jeonggi; Shin, Hyeonjeong; Jang, Jin

doi:10.1021/acsami.8b04721

Cited by 110 publications

(80 citation statements)

References 44 publications

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“…Colloidal II‐VI quantum dots (QDs) have emerged as promising materials for developing efficient light‐emitting diodes (LEDs) for display and lighting applications because of their unique properties such as high photoluminescence (PL) quantum yield (QY), tunable emission color, narrow spectra line width, high photostability and easy solution processability. [ 1–13 ] Recently, advances in chemical synthesis have enabled QDs to show near‐unity PL QY. For example, QDs with a high PL QY of over 90% have been routinely obtained.…”

Section: Introductionmentioning

confidence: 99%

Suppressing Förster Resonance Energy Transfer in Close‐Packed Quantum‐Dot Thin Film: Toward Efficient Quantum‐Dot Light‐Emitting Diodes with External Quantum Efficiency over 21.6%

Zhang

Chen

2020

Advanced Optical Materials

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the presence of Förster resonance energy transfer (FRET) among the close-packed QDs, [19][20][21][22][23][24] which thus limits the efficiency of QD LEDs (QLEDs). FRET is a nonradiative energy transfer process, in which the energy is down-transferred from a fluorescent donor to an acceptor via the dipoledipole coupling if the distance between donor and acceptor is smaller than the transfer radius (typically <10 nm). [24][25][26] In close-packed QD solids, interdot FRET can be very efficient due to the small distance between proximal dots. [25][26][27] Via interdot FRET, excitons therefore can migrate from small dots to nearby large dots, consequently leading to the redshift of the emission spectra. [24,[26][27][28] Along with the redshifted emission, the PL intensity is remarkably decreased, which is caused by the finite probability of nonradiative deactivation whenever an exciton transfers to a new dot with defects. [28] The defective dots function as effective quenching sites that can rapidly quench the excitons of surrounding QDs, leading to the reduction of QY of QD ensembles. Therefore, to improve the PL QY of QD solids, the interdot FRET should be suppressed. Since the FRET rate is very sensitive to the distance between donor and acceptor, [25][26][27]29] we can increase the interdot distance to reduce the FRET rate. This could be realized by tailoring the structure of QDs. For example, by designing giant QDs with thick shell, the devices exhibited an improved performance due to the suppression of interdot FRET. [22,[30][31][32] Alternatively, by embedding the QDs in a polymer matrix, the QDs can be separated spatially, which increases the interdot distance and thereby decreases the interdot FRET. [33][34][35][36][37] However, by physically blending the QDs with polymer, it is difficult to uniformly disperse the QDs within polymer matrix due to phase separation. [33] Recently, by chemically capping the surface of QDs with copolymer, a more homogeneous distribution of QDs is achieved. [34,36] Although increasing the shell thickness or embedding the QDs into a polymer matrix can lead to the suppression of FRET, [22,[30][31][32][33][34] the charge injection and transport are adversely affected by the thick shell or polymer matrix. Therefore, it remains challenging to obtain a device with nearunity internal quantum efficiency (IQE) though QDs with high PL QY of over 90% are routinely reported. Colloidal II-VI quantum dots (QDs) exhibit near-unity photoluminescence (PL) quantum yield (QY) when they are dissolved in dilute solution. However, when they are assembled into thin film, the PL QY is decreased significantly due to the presence of nonradiative Förster resonance energy transfer (FRET) among the close-packed QDs. In this work, the FRET is suppressed by developing a binary-QD light emission layer (EML), where blue-QDs are introduced as spacers to spatially separate the red-QDs. Due to the separation of red-QDs, the FRET among red-QDs is effectively suppressed and thus the emission properties of red-QDs are ...

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Section: Introductionmentioning

confidence: 99%

Suppressing Förster Resonance Energy Transfer in Close‐Packed Quantum‐Dot Thin Film: Toward Efficient Quantum‐Dot Light‐Emitting Diodes with External Quantum Efficiency over 21.6%

Zhang

Chen

2020

Advanced Optical Materials

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“…N-type oxide is an ideal electron transport material and p-type oxide is used as hole injection material for QLEDs. [8][9][10][11] The oxide n-p CGJ is expected to efficiently generate and inject charges to the bottom and top QLEDs under forward bias. 1) The voltage at luminance of 1 cd m -2 .…”

Section: Resultsmentioning

confidence: 99%

47‐3: AMQLED Display with Highly Efficient Oxide N‐P Charge Generation Junction

Kim¹,

Kim²,

Lee³

et al. 2019

Symp Digest of Tech Papers

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We have developed high efficiency tandem quantum-dot lightemitting diode (QLED) by using oxide n-p charge generation junction (CGJ). The tandem QLED with oxide n-p CGJ exhibits the current efficiency as high as over 120 cd A -1 . The oxide n-p CGJ shows good Ohmic behavior under forward and reverse bias. It is obvious that the reverse current density is nearly equal to the forward current density, which suggest the efficient charge generation in the oxide n-p CGJ. In this work, we demonstrated a 4-inch AMQLED display using high efficiency tandem QLED with oxide n-p CGJ. Author KeywordsHigh efficiency, quantum-dot light-emitting diodes, oxide n-p CGJ, tandem structure, 4-inch AMQLED.

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“…The hydroxyl group (-OH) at the surface of the metal oxide layer are the cause of the exciton quenching. 6 The PL intensity increased 5 times when a poly-ethylene oxide layer was deposited at the interface. Moreover, the PEO interlayer improves the wettability of the surface of the substrate with respect to DMSO.…”

Section: Discussion and Conclusion Sectionmentioning

confidence: 99%

P‐9.2: Role of interlayers in inorganic perovskite thin films LEDs

Choi¹,

Kanwat²,

Moyen³

et al. 2019

Symp Digest of Tech Papers

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Here, we report on the reduction of the exciton quenching in inorganic perovskite thin films based LEDs. Using a poly (ethylene oxide) (PEO) interlayer between the perovskite film and the electron transport layer (ETL) results in a 5‐fold improvement of the photo‐luminescence (PL) intensity. Without the interlayer, LEDs do not turn on, while when using an interlayer those exhibit a maximum current efficiency (CE) of 0.8 cd/A with a maximum luminescence (Lmax) of 1300 cd/m2. Moreover, after optimizing thickness of the ETL, moreover, the inorganic PeLEDs exhibit a CE of 7.7 cd/A and a Lmax of 11,300 cd/m2.

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Li and Mg Co-Doped Zinc Oxide Electron Transporting Layer for Highly Efficient Quantum Dot Light-Emitting Diodes

Cited by 110 publications

References 44 publications

Suppressing Förster Resonance Energy Transfer in Close‐Packed Quantum‐Dot Thin Film: Toward Efficient Quantum‐Dot Light‐Emitting Diodes with External Quantum Efficiency over 21.6%

Suppressing Förster Resonance Energy Transfer in Close‐Packed Quantum‐Dot Thin Film: Toward Efficient Quantum‐Dot Light‐Emitting Diodes with External Quantum Efficiency over 21.6%

47‐3: AMQLED Display with Highly Efficient Oxide N‐P Charge Generation Junction

P‐9.2: Role of interlayers in inorganic perovskite thin films LEDs

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