喷墨打印量子点薄膜的形貌控制
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摘要
基于微流体理论,对采用聚合物量子点墨水打印薄膜的干燥过程进行了研究,并通过优化溶剂配比、聚合物含量及干燥温度克服"咖啡环"现象,改善薄膜形貌.研究结果表明:墨水中添加高沸点溶剂有助于延缓外向流动;调节聚合物含量可改变墨水的物理性质,有利于在诱发内向流动的同时阻碍外向流动,二者均可明显改善"咖啡环"形貌,另外聚合物的流平作用可提高薄膜的平整度;调节干燥温度可优化液滴与基板的接触线钉扎,从而进一步改善"咖啡环"形貌.最终,在量子点浓度为12mg/mL,墨水中氯苯/环己基苯体积比为8∶2,聚丙烯酸酯质量百分比为11wt%,干燥温度为25℃时制备了直径约为169μm,高度约为65nm的均匀量子点薄膜及量子点点阵,为QLED器件的制备及Micro-LED面板的全彩化提供了技术支持.
Based on the microfluidic theory,the drying process of film printed with polyacrylate-QD inks was studied.Besides,the coffee ring effect was overcome by optimizing solvent ratio,polymer content and drying temperature to improve the morphology of the array films.The results showed that the addition of high boiling point solvent is helpful to delay the outward flow of droplets on the substrate.Adjusting polymer content can change the physical properties of the inks,which is beneficial to induce inward flow and hinder outward flow.In addition,the polymer can ameliorate the smoothness of the films because of the leveling effect.Both of them can significantly improve the morphology of coffee ring.Moreover,adjusting drying temperature can optimize the pinning of contact line between droplet and substrate,thus further improving the morphology of coffee ring.Finally,the uniform quantum dot films and quantum dot arrays with diameters of 169 μm and heights of 65 nm were prepared at the quantum dot concentration of 12 mg/mL,the volume ratio of chlorobenzene/cyclohexyl benzene in ink is 8∶2,the mass percentage of polyacrylate is 11 wt%,and the drying temperature is 25 ℃,which provides basic technical support for the fabrication of QLED devices and the full-color of Micro-LED panels.
Based on the microfluidic theory,the drying process of film printed with polyacrylate-QD inks was studied.Besides,the coffee ring effect was overcome by optimizing solvent ratio,polymer content and drying temperature to improve the morphology of the array films.The results showed that the addition of high boiling point solvent is helpful to delay the outward flow of droplets on the substrate.Adjusting polymer content can change the physical properties of the inks,which is beneficial to induce inward flow and hinder outward flow.In addition,the polymer can ameliorate the smoothness of the films because of the leveling effect.Both of them can significantly improve the morphology of coffee ring.Moreover,adjusting drying temperature can optimize the pinning of contact line between droplet and substrate,thus further improving the morphology of coffee ring.Finally,the uniform quantum dot films and quantum dot arrays with diameters of 169 μm and heights of 65 nm were prepared at the quantum dot concentration of 12 mg/mL,the volume ratio of chlorobenzene/cyclohexyl benzene in ink is 8∶2,the mass percentage of polyacrylate is 11 wt%,and the drying temperature is 25 ℃,which provides basic technical support for the fabrication of QLED devices and the full-color of Micro-LED panels.
引文
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[24] SOLTMAN D,SUBRAMANIAN V.Inkjet-printed line morphologies and temperature control of the coffee ring effect[J].Langmuir,2008,24(5):2224-2231.
[2] ZAIATS G,IKEDA S,KINGE S,et al.Quantum dot light-emitting devices:beyond alignment of energy levels[J].ACS Applied Materials&Interfaces,2017,9(36):30741-30745.
[3] LIN Huang-Yu,SHER C W,HSIEH D H,et al.Optical cross-talk reduction in a quantum-dot-based full-color microlight-emitting-diode display by a lithographic-fabricated photoresist mold[J].Photonics Research,2017,5(5):411-416.
[4] LI Kai,LIU Jun-kao,CHEN Wei-shan,et al.Controllable printing droplets on demand by piezoelectric inkjet:applications and methods[J].Microsystem Technologies,2018,24(2):879-889.
[5] WEON B M,JE J H.Fingering inside the coffee ring[J].Physical Review E,2013,87(1):013003.
[6] SMALYUKH I I,ZRIBI O V,BUTLER J C,et al.Structure and dynamics of liquid crystalline pattern formation in drying droplets of DNA[J].Physical Review Letters,2006,96(17):177801.
[7] SHMUYLOVICH L,SHEN A Q,STONE H A.Surface morphology of drying latex films:multiple ring formation[J].Langmuir,2002,18(9):3441-3445.
[8] DEEGAN R D,BAKAJIN O,DUPONT T F,et al.Capillary flow as the cause of ring stains from dried liquid drops[J].Nature,1997,389(6653):827.
[9] MAMPALLIL D,ERAL H B.A review on suppression and utilization of the coffee-ring effect[J].Advances in Colloid and Interface Science,2018,252:38-54.
[10] SUN Jia-zhen,BAO Bin,HE Min,et al.Recent advances in controlling the depositing morphologies of inkjet droplets[J].ACS Applied Materials&Interfaces,2015,7(51):28086-28099.
[11] JIANG Cong-biao,ZHONG Zhi-ming,LIU Bai-quan,et al.Coffee-ring-free quantum dot thin film using inkjet printing from a mixed-solvent system on modified ZnO transport layer for light-emitting devices[J].ACS Applied Materials&Interfaces,2016,8(39):26162-26168.
[12] MATAVZ A,FRUNZA R C,DRNOVSEK A,et al.Inkjet printing of uniform dielectric oxide structures from sol–gel inks by adjusting the solvent composition[J].Journal of Materials Chemistry C,2016,4(24):5634-5641.
[13] SEO C,JANG D,CHAE J,et al.Altering the coffee-ring effect by adding a surfactant-like viscous polymer solution[J].Scientific Reports,2017,7(1):500.
[14] YU Xin-hong,XING Ru-bo,PENG Zhong-xiang,et al.To inhibit coffee ring effect in inkjet printing of light-emitting polymer films by decreasing capillary force[J].Chinese Chemical Letters,2019,30(1):135-138.
[15] YUNKER P J,STILL T,LOHR M A,et al.Suppression of the coffee-ring effect by shape-dependent capillary interactions[J].Nature,2011,476(7360):308-311.
[16] LIAN Hong-cheng,QI Lei-hua,LUO Jun,et al.Experimental study and mechanism analysis on the effect of substrate wettability on graphene sheets distribution morphology within uniform printing droplets[J].Journal of Physics:Condensed Matter,2018,30(33):335001.
[17] WU Lei,DONG Zhi-chao,KUANG Min-xuan,et al.Printing patterned fine 3Dstructures by manipulating the three phase contact line[J].Advanced Functional Materials,2015,25(15):2237-2242.
[18] GE Feng,WANG Xiao-hong,ZHANG Yun-feng,et al.Modulating the surface via polymer brush for high-performance inkjet-printed organic thin-film transistors[J].Advanced Electronic Materials,2017,3(1):1600402.
[19] TAO Rui-qiang,NING Hong-long,FANG Zhi-qiang,et al.Homogeneous surface profiles of inkjet-printed silver nanoparticle films by regulating their drying microenvironment[J].Journal of Physical Chemistry C,2017,121(16):8992-8998.
[20] TANNER L H.The spreading of silicone oil drops on horizontal surfaces[J].Journal of Physics D,1979,12(9):1473.
[21] DE GENNES P G.Wetting:statics and dynamics[J].Reviews of Modern Physics,1985,57(3):827.
[22] EFTEKHARI M,FATEMI A.Tensile,creep and fatigue behaviours of short fibre reinforced polymer composites at elevated temperatures:a literature survey[J].Fatigue&Fracture of Engineering Materials&Structures,2015,38(12):1395-1418.
[23] DU Zhong-hui,XING Ru-bo,CAO Xin-xiu,et al.Symmetric and uniform coalescence of ink-jetting printed polyfluorene ink drops by controlling the droplet spacing distance and ink surface tension/viscosity ratio[J].Polymer,2017,115:45-51.
[24] SOLTMAN D,SUBRAMANIAN V.Inkjet-printed line morphologies and temperature control of the coffee ring effect[J].Langmuir,2008,24(5):2224-2231.