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High-performance azure blue quantum dot light-emitting diodes via doping PVK in emitting layer.

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Title: High-performance azure blue quantum dot light-emitting diodes via doping PVK in emitting layer.
Authors: Wang, Lei1, Chen, Tao1, Lin, Qingli1, Shen, Huaibin1 shenhuaibin@henu.edu.cn, Wang, Aqiang1, Wang, Hongzhe1, Li, Chunyang2 lichunyang@zknu.edu.cn, Li, Lin Song1 lsli@henu.edu.cn
Source: Organic Electronics. Oct2016, Vol. 37, p280-286. 7p.
Subjects: Quantum dots, Light emitting diodes, Doping agents (Chemistry), Charge injection, Carbazole, Quantum chemistry, Quantum efficiency
Abstract: Highly bright and efficient azure blue quantum dot-based light-emitting diodes (QD-LEDs) have been demonstrated by employing ZnCdSe core/multishell QDs as emitters and the crucial development we report here is the ability to dramatically enhance the efficiency and brightness through doping poly vinyl( N -carbazole) (PVK) in the emissive layer to balance the charge injection. The best device displays remarkable features like maximum luminance of 13,800 cd/m 2 , luminous efficiency of 6.41 cd/A, and external quantum efficiency (EQE) of 8.76%, without detectable red-shift and broadening in electroluminescence (EL) spectra with increasing voltage as well as good spectral matching between photoluminescence (PL) and EL. Such azure blue quantum-dot LEDs show a 140% increase in external quantum efficiency compared with QD-LEDs without PVK. More important, the peak efficiency of the QD-LEDs with PVK dopant is achieved at luminance of about 1000 cd/m 2 , and high efficiency (EQE > 8%) can be maintained with brightness ranging from 200 to 2400 cd/m 2 . There are two main aspects of the role of PVK in the proposed system. Firstly, the lower HOMO of PVK than (poly[9,9-dioctylfluorene- co - N -[4-(3-methylpropyl)]-diphenylamine] (TFB) can reduce the potential barrier for 0.4 eV at the interface of QDs and hole transport layer which could result in higher hole injection efficiency along with good EQE as compared to TFB-only HTLs. Secondly, with PVK acting as buffer layer of TFB and QDs, the exciton energy transfer from the organic host to the QDs can be effectively improved. [ABSTRACT FROM AUTHOR]
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Database: Engineering Source
Description
Abstract:Highly bright and efficient azure blue quantum dot-based light-emitting diodes (QD-LEDs) have been demonstrated by employing ZnCdSe core/multishell QDs as emitters and the crucial development we report here is the ability to dramatically enhance the efficiency and brightness through doping poly vinyl( N -carbazole) (PVK) in the emissive layer to balance the charge injection. The best device displays remarkable features like maximum luminance of 13,800 cd/m 2 , luminous efficiency of 6.41 cd/A, and external quantum efficiency (EQE) of 8.76%, without detectable red-shift and broadening in electroluminescence (EL) spectra with increasing voltage as well as good spectral matching between photoluminescence (PL) and EL. Such azure blue quantum-dot LEDs show a 140% increase in external quantum efficiency compared with QD-LEDs without PVK. More important, the peak efficiency of the QD-LEDs with PVK dopant is achieved at luminance of about 1000 cd/m 2 , and high efficiency (EQE > 8%) can be maintained with brightness ranging from 200 to 2400 cd/m 2 . There are two main aspects of the role of PVK in the proposed system. Firstly, the lower HOMO of PVK than (poly[9,9-dioctylfluorene- co - N -[4-(3-methylpropyl)]-diphenylamine] (TFB) can reduce the potential barrier for 0.4 eV at the interface of QDs and hole transport layer which could result in higher hole injection efficiency along with good EQE as compared to TFB-only HTLs. Secondly, with PVK acting as buffer layer of TFB and QDs, the exciton energy transfer from the organic host to the QDs can be effectively improved. [ABSTRACT FROM AUTHOR]
ISSN:15661199
DOI:10.1016/j.orgel.2016.06.032