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Cadmium-free quantum dots based violet light-emitting diodes: High-efficiency and brightness via optimization of organic hole transport layers.

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Title: Cadmium-free quantum dots based violet light-emitting diodes: High-efficiency and brightness via optimization of organic hole transport layers.
Authors: Lin, Qingli1,2, Shen, Huaibin2 shenhuaibin@henu.edu.cn, Wang, Hongzhe2, Wang, Aqiang2, Niu, Jinzhong2, Qian, Lei2, Guo, Fang1 fguo@lnu.edu.cn, Li, Lin Song2 lsli@henu.edu.cn
Source: Organic Electronics. Oct2015, Vol. 25, p178-183. 6p.
Subjects: Cadmium compounds, Quantum dots, Zinc sulfide, Fabrication (Manufacturing), Carbazole
Abstract: Bright and efficient violet quantum dot (QD) based light-emitting diodes (QD-LEDs) with heavy-metal-free ZnSe/ZnS have been demonstrated by choosing different hole transport layers, including poly(4-butyl-phenyl-diphenyl-amine) (poly-TPD), poly[9,9-dioctylfluorene-co-N-[4-(3-methylpropyl)]-diphenylamine] (TFB), and poly-N-vinylcarbazole (PVK). Violet QD-LEDs with maximum luminance of about 930 cd/m 2 , the maximum current efficiency of 0.18 cd/A, and the peak EQE of 1.02% when poly-TPD was used as HTL. Higher brightness and low turn-on voltage (3.8 V) violet QD-LEDs could be fabricated when TFB was used as hole transport material. Although the maximum luminance could reach up to 2691 cd/m 2 , the devices exhibited only low current efficiency (∼0.51 cd/A) and EQE (∼2.88%). If PVK is used as hole transport material, highly efficient violet QD-LEDs can be fabricated with lower maximum luminance and higher turn-on voltages compared with counterpart using TFB. Therefore, TFB and PVK mixture in a certain proportion has been used as HTL, turn-on voltage, brightness, and efficiency all have been improved greatly. The QD-LEDs is fabricated with 7.39% of EQE and 2856 cd/m 2 of maximum brightness with narrow FWHM less than 21 nm. These results represent significant improvements in the performance of heavy-metal-free violet QD-LEDs in terms of efficiency, brightness, and color purity. [ABSTRACT FROM AUTHOR]
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Database: Engineering Source
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Abstract:Bright and efficient violet quantum dot (QD) based light-emitting diodes (QD-LEDs) with heavy-metal-free ZnSe/ZnS have been demonstrated by choosing different hole transport layers, including poly(4-butyl-phenyl-diphenyl-amine) (poly-TPD), poly[9,9-dioctylfluorene-co-N-[4-(3-methylpropyl)]-diphenylamine] (TFB), and poly-N-vinylcarbazole (PVK). Violet QD-LEDs with maximum luminance of about 930 cd/m 2 , the maximum current efficiency of 0.18 cd/A, and the peak EQE of 1.02% when poly-TPD was used as HTL. Higher brightness and low turn-on voltage (3.8 V) violet QD-LEDs could be fabricated when TFB was used as hole transport material. Although the maximum luminance could reach up to 2691 cd/m 2 , the devices exhibited only low current efficiency (∼0.51 cd/A) and EQE (∼2.88%). If PVK is used as hole transport material, highly efficient violet QD-LEDs can be fabricated with lower maximum luminance and higher turn-on voltages compared with counterpart using TFB. Therefore, TFB and PVK mixture in a certain proportion has been used as HTL, turn-on voltage, brightness, and efficiency all have been improved greatly. The QD-LEDs is fabricated with 7.39% of EQE and 2856 cd/m 2 of maximum brightness with narrow FWHM less than 21 nm. These results represent significant improvements in the performance of heavy-metal-free violet QD-LEDs in terms of efficiency, brightness, and color purity. [ABSTRACT FROM AUTHOR]
ISSN:15661199
DOI:10.1016/j.orgel.2015.06.032