Bright hybrid white light-emitting quantum dot device with direct charge injection into quantum dot*

A bright white quantum dot light-emitting device (white-QLED) with 4-[4-(1-phenyl-1H-benzo[d]imidazol-2-yl)phenyl]-2- [3-(tri-phenylen-2-yl)phen-3-yl]quinazoline deposited on a thin film of mixed green/red-QDs as a bilayer emitter is fabricated. The optimized white-QLED exhibits a turn-on voltage of 3.2 V and a maximum brightness of 3660 cd/m2@8 V with the Commission Internationale de l'Eclairage (CIE) chromaticity in the region of white light. The ultra-thin layer of QDs is proved to be critical for the white light generation in the devices. Excitation mechanism in the white-QLEDs is investigated by the detailed analyses of electroluminescence (EL) spectral and the fluorescence lifetime of QDs. The results show that charge injection is a dominant mechanism of excitation in the white-QLED.

[1]  D. Y. Yoon,et al.  Bright and efficient full-color colloidal quantum dot light-emitting diodes using an inverted device structure. , 2012, Nano letters.

[2]  Cherie R. Kagan,et al.  Electronic energy transfer in CdSe quantum dot solids. , 1996, Physical review letters.

[3]  V. Bulović,et al.  NiO as an inorganic hole-transporting layer in quantum-dot light-emitting devices. , 2006, Nano letters.

[4]  Lei Ding,et al.  High-Performance Hybrid White Organic Light-Emitting Diodes Utilizing a Mixed Interlayer as the Universal Carrier Switch , 2015 .

[5]  X. W. Sun,et al.  Colloidal Quantum Dot Light-Emitting Diodes Employing Phosphorescent Small Organic Molecules as Efficient Exciton Harvesters. , 2014, The journal of physical chemistry letters.

[6]  Kookheon Char,et al.  Single-Step Synthesis of Quantum Dots with Chemical Composition Gradients , 2008 .

[7]  D. Kwon,et al.  Highly Efficient White Light-Emitting Diodes Based on Quantum Dots and Polymer Interface , 2012, IEEE Photonics Technology Letters.

[8]  Chaoxing Wu,et al.  Improved performance of flexible white hybrid light emitting diodes by adjusting quantum dots distribution in polymer matrix , 2015 .

[9]  Yizheng Jin,et al.  Solution-processed, high-performance light-emitting diodes based on quantum dots , 2014, Nature.

[10]  White light-emitting organic device with electroluminescent quantum dots and organic molecules , 2009 .

[11]  V. Bulović,et al.  Electroluminescence from a mixed red-green-blue colloidal quantum dot monolayer. , 2007, Nano letters.

[12]  P. Holloway,et al.  Stable and efficient quantum-dot light-emitting diodes based on solution-processed multilayer structures , 2011 .

[13]  Yongwoo Kwon,et al.  Over 40 cd/A efficient green quantum dot electroluminescent device comprising uniquely large-sized quantum dots. , 2014, ACS nano.

[14]  Cherie R. Kagan,et al.  Long-range resonance transfer of electronic excitations in close-packed CdSe quantum-dot solids. , 1996, Physical review. B, Condensed matter.

[15]  Byoung-Ho Kang,et al.  Highly efficient hybrid light-emitting device using complex of CdSe/ZnS quantum dots embedded in co-polymer as an active layer. , 2010, Optics express.

[16]  A. Alivisatos,et al.  Light-emitting diodes made from cadmium selenide nanocrystals and a semiconducting polymer , 1994, Nature.

[17]  S. Yue,et al.  Shifting the light emitting component from core to shell: an effective approach to improve the efficiency of light-emitting diodes based on multi-junction quantum materials. , 2015, Nanoscale.

[18]  Yongfang Li,et al.  Bright, multicoloured light-emitting diodes based on quantum dots , 2007 .

[19]  Andrew Wang,et al.  Inverted CdSe/CdS/ZnS quantum dot light emitting devices with titanium dioxide as an electron-injection contact. , 2013, Nanoscale.

[20]  Ki-Heon Lee,et al.  Highly efficient, color-pure, color-stable blue quantum dot light-emitting devices. , 2013, ACS nano.

[21]  Ying Zhang,et al.  High-quality violet- to red-emitting ZnSe/CdSe core/shell nanocrystals , 2005 .

[22]  J. Ruzyllo,et al.  Stable Binary Complementary White Light-Emitting Diodes Based on Quantum-Dot/Polymer-Bilayer Structures , 2008, IEEE Photonics Technology Letters.

[23]  G. Gigli,et al.  White light-emitting devices based on the combined emission from red CdSe/ZnS quantum dots, green phosphorescent, and blue fluorescent organic molecules , 2009 .

[24]  Wenyu Ji,et al.  Efficient energy transfer from hole transporting materials to CdSe-core CdS/ZnCdS/ZnS-multishell quantum dots in type II aligned blend films , 2011 .