High-Efficiency Phosphorescent Hybrid Organic–Inorganic Light-Emitting Diodes Using a Solution-Processed Small-Molecule Emissive Layer

Fan, Changjun; Lei, Yong; Liu, Zhen; Wang, Ruixue; Lei, Yanlian; Li, Guoqing; Xiong, Zuhong; Yang, Xiaohui

doi:10.1021/acsami.5b05815

Cited by 28 publications

(21 citation statements)

References 49 publications

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“…The triplet diagram in Fig. 2g shows that host-to-guest Dexter transfer is feasible for all host systems 48 , 49 , while the significant spectral overlap of the host photoluminescence (PL) and the guest absorption displayed in Fig. 2h implies that host-to-guest Förster resonance transfer can be efficient for all three host–guest systems.…”

Section: Resultsmentioning

confidence: 99%

Design rules for light-emitting electrochemical cells delivering bright luminance at 27.5 percent external quantum efficiency

et al. 2017

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The light-emitting electrochemical cell promises cost-efficient, large-area emissive applications, as its characteristic in-situ doping enables use of air-stabile electrodes and a solution-processed single-layer active material. However, mutual exclusion of high efficiency and high brightness has proven a seemingly fundamental problem. Here we present a generic approach that overcomes this critical issue, and report on devices equipped with air-stabile electrodes and outcoupling structure that deliver a record-high efficiency of 99.2 cd A−1 at a bright luminance of 1910 cd m−2. This device significantly outperforms the corresponding optimized organic light-emitting diode despite the latter employing calcium as the cathode. The key to this achievement is the design of the host–guest active material, in which tailored traps suppress exciton diffusion and quenching in the central recombination zone, allowing efficient triplet emission. Simultaneously, the traps do not significantly hamper electron and hole transport, as essentially all traps in the transport regions are filled by doping.

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Section: Resultsmentioning

confidence: 99%

Design rules for light-emitting electrochemical cells delivering bright luminance at 27.5 percent external quantum efficiency

et al. 2017

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“…One fundamental difference between evaporated and solution processed films is the molecular packing. As summarized in Table S1 of the Supporting Information, it is generally accepted that solution processed organic films have a lower packing density than the vacuum deposited films. Previous studies comparing solution processed and evaporated OLEDs were mostly focused on HTLs, where the packing density and hence carrier transport plays a critical role .…”

Section: Introductionmentioning

confidence: 99%

“…As summarized in Table S1 of the Supporting Information, it is generally accepted that solution processed organic films have a lower packing density than the vacuum deposited films. Previous studies comparing solution processed and evaporated OLEDs were mostly focused on HTLs, where the packing density and hence carrier transport plays a critical role . On the other hand, there are only a few reports directly comparing the performance of devices with solution processed and evaporated phosphorescent EMLs, and the root cause for the difference in device performance is not well understood.…”

Section: Introductionmentioning

confidence: 99%

Interface Effect on Efficiency Loss in Organic Light Emitting Diodes with Solution Processed Emitting Layers

Chen

Liu

et al. 2016

Adv Materials Inter

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easily achieved with sequential deposition, the redissolution of the preceding layer by solvents used in the subsequent layers is a challenge for solution processed OLEDs during the multilayer fabrication process. [ 4 ] To get around this problem, cross-linkable hole transporting layers (HTLs) are typically used such that subsequent deposition of the emitting layer (EML) would not damage the underlying HTL during processing. [5][6][7][8][9][10][11] To fi nish the device fabrication, evaporated electron transport layers (ETLs) are used in OLED fabrication to avoid solvent damages to the EML.Even with the same multilayer architecture, most OLEDs with a solution processed EML have lower effi ciencies than their thermal-evaporated counterparts. [12][13][14][15][16][17] One fundamental difference between evaporated and solution processed fi lms is the molecular packing. As summarized in Table S1 of the Supporting Information, [16][17][18][19][20][21][22][23][24][25][26] it is generally accepted that solution processed organic fi lms have a lower packing density than the vacuum deposited fi lms. Previous studies comparing solution processed and evaporated OLEDs were mostly focused on HTLs, where the packing density and hence carrier transport plays a critical role. [ 18,20,25,26 ] On the other hand, there are only a few reports directly comparing the performance of devices with solution processed and evaporated phosphorescent EMLs, [ 17,19 ] and the root cause for the difference in device performance is not well understood. It is, therefore, important to identify and study the factors determining the effi ciency loss mechanism in devices with a solution processed EML.In this work, we study the differences in high effi ciency OLEDs having solution processed and thermal-evaporated EMLs. Similar to other fi ndings, we found that the EQE of OLEDs with a solution processed EML is 22% lower than that of the devices with an evaporated EML using 1,3,5tris (N-phenylbenzimidazol-2,yl) benzene (TPBi) as an ETL. Interestingly, this difference in effi ciency became signifi cantly smaller as TPBi was replaced with bis -4,6-(3,5-di-3-pyridylphenyl)-2-methylpyrimidine (B3PYMPM) as an alternative ETL. Because of the deep highest occupied molecular orbital (HOMO) energy of B3PYMPM, we attribute the lower effi ciency in OLEDs with solution processed EMLs to the ineffi cient hole blocking properties of the TPBi ETL as revealed by the single carrier device results. A subsequent study on interfacial exciplex formation and energetic disorder revealed that for devices with a solution processed EML, band tail states broadening along with an energy level shift at the EML/ETL interfaces results in a higherThe performance of multilayered OLEDs with a solution processed emitting layer (EML) is compared to that of counterparts with an evaporated EML and it is found that the interfacial energy changes at the EML and electron transport layer (ETL) interface is a key factor determining the device effi ciency. From the results of exciplex photoluminesc...

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“…Future work should focus on replacing poly‐TPD with a highly emissive organic HTL to combine with the perovskite materials, which should enhance the efficiency and stability further. [ 28–31 ]…”

Section: Resultsmentioning

confidence: 99%

Tunable Electroluminescence for Pure White Emission From a Perovskite‐Based LED

Vashishtha

Brown

et al. 2021

Adv Elect Materials

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Halide perovskite nanocrystals are a promising candidate for lighting applications. However, the production of white light emitting diodes (LEDs) is still a major challenge due to halide ion segregation. In this work, it is demonstrated that reducing the thickness of the perovskite layer in an LED stack can modulate the recombination zone, such that a tunable emission can be obtained. This comprises of an orange electromer emission from a hole‐transport layer (HTL), green electroluminescence from the perovskite active layer, and a blue monomer emission from the same HTL. Overall, a pure white emission can be achieved after successful device optimization, which is particularly challenging for LEDs in which the emission originates solely from perovskite layer. It is anticipated that this methodology could be employed on any type of green‐emitting nanocrystals to fabricate white LEDs.

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High-Efficiency Phosphorescent Hybrid Organic–Inorganic Light-Emitting Diodes Using a Solution-Processed Small-Molecule Emissive Layer

Cited by 28 publications

References 49 publications

Design rules for light-emitting electrochemical cells delivering bright luminance at 27.5 percent external quantum efficiency

Design rules for light-emitting electrochemical cells delivering bright luminance at 27.5 percent external quantum efficiency

Interface Effect on Efficiency Loss in Organic Light Emitting Diodes with Solution Processed Emitting Layers

Tunable Electroluminescence for Pure White Emission From a Perovskite‐Based LED

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