scholarly journals Suppression of Electric Field-Induced Segregation in Sky-Blue Perovskite Light-Emitting Electrochemical Cells

Nanomaterials ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 1937
Author(s):  
Tatiana G. Liashenko ◽  
Anatoly P. Pushkarev ◽  
Arnas Naujokaitis ◽  
Vidas Pakštas ◽  
Marius Franckevičius ◽  
...  
Keyword(s):  
Electric Field ◽  
Band Gap ◽  
Quantum Efficiency ◽  
External Quantum Efficiency ◽  
Film Deposition ◽  
Infrared Light ◽  
Electrochemical Cells ◽  
Light Emitting ◽  
Light Emitting Devices ◽  
Turn On

Inexpensive perovskite light-emitting devices fabricated by a simple wet chemical approach have recently demonstrated very prospective characteristics such as narrowband emission, low turn-on bias, high brightness, and high external quantum efficiency of electroluminescence, and have presented a good alternative to well-established technology of epitaxially grown III-V semiconducting alloys. Engineering of highly efficient perovskite light-emitting devices emitting green, red, and near-infrared light has been demonstrated in numerous reports and has faced no major fundamental limitations. On the contrary, the devices emitting blue light, in particular, based on 3D mixed-halide perovskites, suffer from electric field-induced phase separation (segregation). This crystal lattice defect-mediated phenomenon results in an undesirable color change of electroluminescence. Here we report a novel approach towards the suppression of the segregation in single-layer perovskite light-emitting electrochemical cells. Co-crystallization of direct band gap CsPb(Cl,Br)3 and indirect band gap Cs4Pb(Cl,Br)6 phases in the presence of poly(ethylene oxide) during a thin film deposition affords passivation of surface defect states and an increase in the density of photoexcited charge carriers in CsPb(Cl,Br)3 grains. Furthermore, the hexahalide phase prevents the dissociation of the emissive grains in the strong electric field during the device operation. Entirely resistant to 5.7 × 106 V·m−1 electric field-driven segregation light-emitting electrochemical cell exhibits stable emission at wavelength 479 nm with maximum external quantum efficiency 0.7%, maximum brightness 47 cd·m−2, and turn-on bias of 2.5 V.

scholarly journals Pyridinyl-Carbazole Fragments Containing Host Materials for Efficient Green and Blue Phosphorescent OLEDs

Molecules ◽  
2021 ◽  
Vol 26 (15) ◽  
pp. 4615
Author(s):  
Dovydas Blazevicius ◽  
Daiva Tavgeniene ◽  
Simona Sutkuviene ◽  
Ernestas Zaleckas ◽  
Ming-Ruei Jiang ◽  
...  
Keyword(s):  
Current Efficiency ◽  
Quantum Efficiency ◽  
External Quantum Efficiency ◽  
Power Efficiency ◽  
Triplet Energy ◽  
New Host ◽  
High Brightness ◽  
Light Emitting ◽  
Light Emitting Devices ◽  
Host Materials

Pyridinyl-carbazole fragments containing low molar mass compounds as host derivatives H1 and H2 were synthesized, investigated, and used for the preparation of electro-phosphorescent organic light-emitting devices (PhOLEDs). The materials demonstrated high stability against thermal decomposition with the decomposition temperatures of 361–386 °C and were suitable for the preparation of thin amorphous and homogeneous layers with very high values of glass transition temperatures of 127–139 °C. It was determined that triplet energy values of the derivatives are, correspondingly, 2.82 eV for the derivative H1 and 2.81 eV for the host H2. The new derivatives were tested as hosts of emitting layers in blue, as well as in green phosphorescent OLEDs. The blue device with 15 wt.% of the iridium(III)[bis(4,6-difluorophenyl)-pyridinato-N,C2′]picolinate (FIrpic) emitter doping ratio in host material H2 exhibited the best overall characteristics with a power efficiency of 24.9 lm/W, a current efficiency of 23.9 cd/A, and high value of 10.3% of external quantum efficiency at 100 cd/m2. The most efficient green PhOLED with 10 wt% of Ir(ppy)3 {tris(2-phenylpyridine)iridium(III)} in the H2 host showed a power efficiency of 34.1 lm/W, current efficiency of 33.9 cd/A, and a high value of 9.4% for external quantum efficiency at a high brightness of 1000 cd/m2, which is required for lighting applications. These characteristics were obtained in non-optimized PhOLEDs under an ordinary laboratory atmosphere and could be improved in the optimization process. The results demonstrate that some of the new host materials are very promising components for the development of efficient phosphorescent devices.

Air-processed stable near-infrared Si-based perovskite light-emitting devices with efficiency exceeding 7.5%

2022 ◽  
Author(s):  
Xiaoxiao Xu ◽  
Ke Xiao ◽  
Guozhi Hou ◽  
Yu Zhu ◽  
Ting Zhu ◽  
...  
Keyword(s):  
Quantum Efficiency ◽  
External Quantum Efficiency ◽  
Near Infrared ◽  
Ambient Air ◽  
Light Emitting ◽  
Light Emitting Devices ◽  
Composite Layers

Two composite layers are used to enhance the efficiency of Si-based near-infrared perovskite light-emitting devices, which are produced in ambient air, and the external quantum efficiency increased to 7.5%.

High-efficiency, deep blue ZnCdS/CdxZn1−xS/ZnS quantum-dot-light-emitting devices with an EQE exceeding 18%

Nanoscale ◽  
2018 ◽  
Vol 10 (12) ◽  
pp. 5650-5657 ◽  
Author(s):  
Ouyang Wang ◽  
Lei Wang ◽  
Zhaohan Li ◽  
Qiulei Xu ◽  
Qingli Lin ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Quantum Dot ◽  
Quantum Efficiency ◽  
External Quantum Efficiency ◽  
High Efficiency ◽  
Light Emitting ◽  
Light Emitting Devices ◽  
Deep Blue

18% peak external quantum efficiency (EQE) for deep blue QLEDs by using ZnCdS/CdxZn1−xS/ZnS quantum dots.

High-performance narrow spectrum green phosphorescent top-emitting organic light-emitting devices with external quantum efficiency up to 38%

2021 ◽  
Author(s):  
Xiaokang Li ◽  
Wenxing Liu ◽  
Kai Chen ◽  
Ruixia Wu ◽  
Guo-Jun Liu ◽  
...  
Keyword(s):  
Quantum Efficiency ◽  
External Quantum Efficiency ◽  
High Performance ◽  
Cavity Length ◽  
Strong Dependence ◽  
Emission Peak ◽  
Light Emitting ◽  
Light Emitting Devices ◽  
Organic Light ◽  
Micro Cavity

Abstract In this work, we have experimentally demonstrated the efficacy of micro-cavity effect in realizing high-performance top-emitting organic light-emitting diodes (TEOLEDs). By optimizing the thickness of top Yb/Ag electrode and cavity length, highly efficient green TEOLED with external quantum efficiency as high as 38% was achieved. A strong dependence of electroluminescent (EL) performances and spectrum on cavity length was observed, and there was also a significant angle dependence of EL spectrum. Ultimately, ultra-high current efficiency up to 161.17 cd/A (3.2 V) was obtained by the device with emission peak at 552 nm, which is 35 nm longer than the intrinsic emission peak (517 nm) of utilized green emitter. Interestingly, this device displayed narrow emission with full-width at half-maximum (FWHM) of less than 20 nm, which was obtained by increasing the Ag layer thickness.

scholarly journals Thermally activated delayed fluorescence with 7% external quantum efficiency from a light-emitting electrochemical cell

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Petter Lundberg ◽  
Youichi Tsuchiya ◽  
E. Mattias Lindh ◽  
Shi Tang ◽  
Chihaya Adachi ◽  
...  
Keyword(s):  
Quantum Efficiency ◽  
External Quantum Efficiency ◽  
Active Material ◽  
Fluorescence Emission ◽  
Single Layer ◽  
Delayed Fluorescence ◽  
Electrochemical Cells ◽  
Thermally Activated Delayed Fluorescence ◽  
Light Emitting ◽  
Thermally Activated

AbstractWe report on light-emitting electrochemical cells, comprising a solution-processed single-layer active material and air-stabile electrodes, that exhibit efficient and bright thermally activated delayed fluorescence. Our optimized devices delivers a luminance of 120 cd m−2 at an external quantum efficiency of 7.0%. As such, it outperforms the combined luminance/efficiency state-of-the art for thermally activated delayed fluorescence light-emitting electrochemical cells by one order of magnitude. For this end, we employed a polymeric blend host for balanced electrochemical doping and electronic transport as well as uniform film formation, an optimized concentration (<1 mass%) of guest for complete host-to-guest energy transfer at minimized aggregation and efficient emission, and an appropriate concentration of an electrochemically stabile electrolyte for desired doping effects. The generic nature of our approach is manifested in the attainment of bright and efficient thermally activated delayed fluorescence emission from three different light-emitting electrochemical cells with invariant host:guest:electrolyte number ratio.

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