Ultrahighly Efficient White Quantum Dot Light‐Emitting Diodes Operating at Low Voltage

Zhu, Yuan; Xu, Rui; Zhou, Yuangui; Xu, Zhiai; Liu, Yang; Tian, Fengqing; Zheng, X. H.; Ma, Fumin; Alsharafi, Rashed; Hu, Hailong; Guo, Tailiang; Kim, Tae Whan; Li, Fushan

doi:10.1002/adom.202001479

Cited by 31 publications

(25 citation statements)

References 34 publications

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“…[ 46–49 ] The significant EQE roll‐off of the WQLED based on CNPr‐TFB is mainly due to the poor performance of blue QLED at high applied voltages as discussed above, which is also found in other literature reports. [ 46,50 ] Therefore, from these results, it is noted that the hole‐transporting polymer CNPr‐TFB is superior to the commonly used TFB HTL in the WQLED applications.…”

Section: Resultsmentioning

confidence: 93%

An Efficient Hole Transporting Polymer for Quantum Dot Light‐Emitting Diodes

Chen

Zhan

et al. 2021

Adv Materials Inter

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Ideal hole transporting polymers used in quantum dot (QD) light‐emitting diodes (QLEDs) should possess the features such as high conductivities and stabilized highest occupied molecular orbitals (HOMOs). Herein, an efficient polymer (named CNPr‐TFB) is achieved by rationally adding a relatively weak electron‐withdrawing group (2‐cyanopropan‐2‐yl, CNPr) on a TFB like hole transporting polymer. CNPr‐TFB exhibits a superior hole conductivity and much more stabilized HOMO in comparison with TFB. Therefore, much more holes are delivered into the QD emissive layers and a balanced recombination of electron and hole in the QLEDs is achieved. The external quantum efficiencies of the red, green, blue, and white QLEDs made by CNPr‐TFB as the hole transporting layer (HTL) are 20.7%, 16.6%, 11.3%, and 15.0%, respectively, which are increased by 1.4–2.3 times in comparison with those of devices based on the commonly used TFB HTL. Meanwhile, the CNPr‐TFB‐based QLEDs also exhibit longer operation lifetimes than those of devices using the TFB HTL. These results confirm that CNPr‐TFB with the features of high conductivity and stabilized HOMO can be an excellent HTL material for the QLED applications

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Section: Resultsmentioning

confidence: 93%

An Efficient Hole Transporting Polymer for Quantum Dot Light‐Emitting Diodes

Chen

Zhan

et al. 2021

Adv Materials Inter

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“…In order to realize commercial application for QLEDs in general illumination and displays, white QLEDs should be developed [21,[27][28][29]. Till present, there are two main methods to fabricate white QLEDs, namely, red-green-blue (RGB) QDs mixing and RGB QD layers stacking.…”

Section: Resultsmentioning

confidence: 99%

Efficient quantum dot light-emitting diodes with ultra-homogeneous and highly ordered quantum dot monolayer

et al. 2021

Self Cite

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Regarding conventional quantum dot lightemitting diodes (QLEDs) fabricated by using the spin-coating (SC) technique, voids and interstitial spaces are inevitable due to unordered quantum dots (QDs) stacking, generating device leakage current under an external bias. In the present study, we fabricated an ultra-homogeneous and highly ordered QD monolayer by adopting the Langmuir-Blodgett (LB) technique. The QD monolayer was transferred as a emissive layer with a horizontal lifting (HL) method to a red QLED, which exhibited high performance with an external quantum efficiency (EQE) of 19.0% and lifetime (T 95 @100 cd m −2 ) of 13,324 h. When compared with the SC-based device, the EQE and lifetime were improved by 15% and 183% due to the compact and ordered QD monolayer that lowered the leakage current. Moreover, white QLEDs with stacked QD monolayers could be obtained at a low voltage of 4 V because LB technique is an organic-solvent-free approach avoiding interlayer mixing and controlling the QD layer thickness precisely. In addition, we successfully fabricated an ultra-homogeneous large-area QD monolayer on a rectangular substrate with a size of 9 cm × 5 cm, indicating the promising size scalability of the LB-HL strategy.

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“…This is due to the FRET from blue to green and red QDs, which is well consistent with the PLQY measurement, that is, when the mixed QDs formed a QD layer, PLQY of blue QDs significantly decreased as FRET increased due to the reduced dot-to-dot distance which was discussed in Figure 1. [21][22][23][24][25][26]28] However, the severe imbalance of the RGB ratio leads to degradation of white QLED performance because a turn-on voltage of a QLED would increase due to the high ratio of blue QDs with the larger bandgap as evidenced by the turn-on voltage of warm and daylight white QLEDs in Table 1. Therefore, smaller amount of blue QDs is desirable with the same CCT value.…”

Section: Resultsmentioning

confidence: 99%

“…[ 23,27 ] As a result, a much higher volume of blue QDs were required than that of green and red QDs in the mixed QD solution for white light emission evidenced by the RGB mixing ratio 1:2:9, which is well consistent with previous reports that employed larger fraction of the QDs with higher bandgap than the QDs with lower bandgap. [ 19,23,28 ]…”

Section: Resultsmentioning

confidence: 99%

Enhanced Direct White Light Emission Efficiency in Quantum Dot Light‐Emitting Diodes via Embedded Ferroelectric Islands Structure

Cho

Pak

et al. 2021

Adv Funct Materials

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White light emission is of great importance in our daily life as it is the primary source of light indoor and outdoor as well as day and night. Among various materials and lighting technologies, intensive efforts have been made to quantum dots based-light-emitting diode (QD-LEDs, or QLEDs) because of outstanding optical properties, facile synthesis, and bandgap tunability of QDs. Despite the fact that QLEDs are able to present various colors in a visible range, realizing efficient direct white light emission is a challenge as white light emission can only be achievable through stacking and patterning of QD films or mixing of different sizes of QDs. This inevitably involves energy band mismatch at interfaces, leading to degradation of device performance. Here, a new effective method to improve white QLED performances through embedding a ferroelectric islands structure is introduced, which induces an electric field to effectively modulate the energy band at the junction interface. The formation of a favorable energy landscape leads to efficient charge transport, improved radiative recombination, and consequently high external quantum efficiency in the white QLEDs. In addition, it is demonstrated that this new approach is proved to be effective in different color temperatures ranging from 3000 to over 120 000 K.

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Ultrahighly Efficient White Quantum Dot Light‐Emitting Diodes Operating at Low Voltage

Cited by 31 publications

References 34 publications

An Efficient Hole Transporting Polymer for Quantum Dot Light‐Emitting Diodes

An Efficient Hole Transporting Polymer for Quantum Dot Light‐Emitting Diodes

Efficient quantum dot light-emitting diodes with ultra-homogeneous and highly ordered quantum dot monolayer

Enhanced Direct White Light Emission Efficiency in Quantum Dot Light‐Emitting Diodes via Embedded Ferroelectric Islands Structure

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