混合量子点QLED结构性能研究
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摘要
为研究基于混合量子点的QLED结构与性能,利用红光量子点以及绿光量子点两种材料制备了橙光QLED器件,并对其性能进行了表征。实验制备的器件结构为ITO/PEDOT∶PSS/poly-TPD/混合QDs/Zn O/Al,其中发光层采用了3种混合量子点的混合结构方案。方案一先旋涂红光量子点层,后旋涂绿光量子点层;方案二先旋涂绿光量子点层,后旋涂红光量子点层;方案三将红光、绿光量子点1∶1混合后制备为发光层。实验结果表明:方案一制备的器件电流密度最大,发光亮度最低,且只有红光谱;方案二制备的器件具有最小的电流密度,同时具有红、绿光谱,在8 V电压下,电流效率约为4.69 cd/A;方案三制备的器件同时具有红、绿光谱,电流密度与发光特性介于方案一与方案二之间。实测数据与理论分析是一致的,方案二制备的器件存在双能量陷阱,能够将注入的空穴以及电子同时限制在红光量子点层内。通过调节各功能层厚度使得载流子注入平衡,可进一步增大发光电流,提高器件效率。
In order to study the structure and properties of QLED based on hybrid quantum dots,QLED devices were prepared using red light quantum dots and green light quantum dots as the lightemitting layer,and their properties were characterized. The structure of the device fabricated was ITO/PEDOT∶ PSS/poly-TPD/hybrid QDs/Zn O/Al,in which three kinds of hybrid quantum dot light-emitting layer were adopted. The red light quantum dot layer was spin coated firstly in the solution 1,followed with spin-coating green light quantum dot layer. The solution 2 first spin-coated green light quantum point layer,red quantum dot layer was spin-coated after that. In the solution 3,red and green quantum dots were mixed with the proportion of 1∶ 1 and was then spin-coated as the light-emitting layer. The experimental results show that the device prepared by the solution 1 has the largest current density,lowest luminous intensity and only exhibit red light. The device prepared by the solution 2 has the minimum current density,and has the spectra of both red and green light. The maximum current efficiency is 4. 69 cd/A at the external bias of 8 V. The device prepared by the solution 3 also exhibits red and green light,the current density and the luminous intensity are lower than that of the device prepared by the solution 2. It can be concluded from the energy level that the device prepared by the solution 2 has a double energy trap,therefore,it is advantageous in trappingboth holes and electrons to the red light quantum dot layer. It is achievable to further improve the device efficiency by adjusting the thickness of each functional layer to balance the carrier injection.
In order to study the structure and properties of QLED based on hybrid quantum dots,QLED devices were prepared using red light quantum dots and green light quantum dots as the lightemitting layer,and their properties were characterized. The structure of the device fabricated was ITO/PEDOT∶ PSS/poly-TPD/hybrid QDs/Zn O/Al,in which three kinds of hybrid quantum dot light-emitting layer were adopted. The red light quantum dot layer was spin coated firstly in the solution 1,followed with spin-coating green light quantum dot layer. The solution 2 first spin-coated green light quantum point layer,red quantum dot layer was spin-coated after that. In the solution 3,red and green quantum dots were mixed with the proportion of 1∶ 1 and was then spin-coated as the light-emitting layer. The experimental results show that the device prepared by the solution 1 has the largest current density,lowest luminous intensity and only exhibit red light. The device prepared by the solution 2 has the minimum current density,and has the spectra of both red and green light. The maximum current efficiency is 4. 69 cd/A at the external bias of 8 V. The device prepared by the solution 3 also exhibits red and green light,the current density and the luminous intensity are lower than that of the device prepared by the solution 2. It can be concluded from the energy level that the device prepared by the solution 2 has a double energy trap,therefore,it is advantageous in trappingboth holes and electrons to the red light quantum dot layer. It is achievable to further improve the device efficiency by adjusting the thickness of each functional layer to balance the carrier injection.
引文
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[3]SCHLAMP M C,PENG X G,ALIVISATOS A P.Improved efficiencies in light emitting diodes made with Cd Se(Cd S)core/shell type nanocrystals and a semiconducting polymer[J].J.Appl.Phys.,1997,82(11):5837-5842.
[4]陈雯柏,叶继兴,马航,等.一种QLEDs功能层厚度确定方法[J].光子学报,2017,46(5):1-9.CHEN W B,YE J X,MA H,et al..Thickness estimation method for every functional layer of QLEDs[J].Acta Photon.Sinica,2017,46(5):1-9.(in Chinese)
[5]SUPRAN G J,SHIRASAKI Y,SONG K W,et al..QLEDs for displays and solid-state lighting[J].MRS Bull.,2013,38(9):703-711.
[6]KONSTANTATOS G,HOWARD I,FISCHER A,et al..Ultrasensitive solution-cast quantum dot photodetectors[J].Nature,2006,442(7099):180-183.
[7]COLVIN V L,SCHLAMP M C,ALIVISATOS A P.Light-emitting diodes made from cadmium selenide nanocrystals and a semiconducting polymer[J].Nature,1994,370(6488):354-357.
[8]CHO K S,LEE E K,JOO W J,et al..High-performance crosslinked colloidal quantum-dot light-emitting diodes[J].Nat.Photon.,2009,3(6):341-345.
[9]彭辉仁,陈树明,王忆.基于聚合物-量子点共混的量子点发光二极管[J].发光学报,2016,37(3):299-304.PENG H R,CHEN S M,WANG Y.Quantum dot light-emitting diodes with mixed polymer-quantum dots light-emitting layer[J].Chin.J.Lumin.,2016,37(3):299-304.(in Chinese)
[10]SUN Q J,WANG Y A,LI L S,et al..Bright,multicoloured light-emitting diodes based on quantum dots[J].Nat.Photon.,2007,1(12):717-722.
[11]ANIKEEVA P O,HALPERT J E,BAWENDI M G,et al..Quantum dot light-emitting devices with electroluminescence tunable over the entire visible spectrum[J].Nano Lett.,2009,9(7):2532-2536.
[12]QIAN L,ZHENG Y,XUE J G,et al..Stable and efficient quantum-dot light-emitting diodes based on solution-processed multilayer structures[J].Nat.Photon.,2011,5(9):543-548.
[13]DAI X L,ZHANG Z X,JIN Y Z,et al..Solution-processed,high-performance light-emitting diodes based on quantum dots[J].Nature,2014,515(7525):96-99.
[14]BAE W K,LIM J,LEE D,et al..R/G/B/natural white light thin colloidal quantum dot-based light-emitting devices[J].Adv.Mater.,2014,26(37):6387-6393.
[15]LEE J S,KANG B H,KIM S H,et al..All-solution-processed high-brightness hybrid white quantum-dot light-emitting devices utilizing polymer modified quantum dots[J].Org.Electron.,2017,42:393-398.
[16]JI W Y,TIAN Y,ZENG Q H,et al..Efficient quantum dot light-emitting diodes by controlling the carrier accumulationand exciton formation[J].ACS Appl.Mater.Interf.,2014,6(16):14001-14007.
[17]ANIKEEVA P O.Physical Properties and Design of Light-emitting Devices Based on Organic Materials and Nanoparticles[D].Massachusetts:Massachusetts Institute of Technology,2009.
[18]黄维,密保秀,高志强.有机电子学[M].北京:科学出版社,2011.HUANG W,MI B X,GAO Z Q.Organic Electronics[M].Beijing:Science Press,2011.(in Chinese)