J. Phys. Chem. C 2010, 114, 9883–9888
9883
Patterning of Light-Emitting YVO4:Eu3+ Thin Films via Inkjet Printing Ziyong Cheng,† Rubo Xing,‡ Zhiyao Hou,† Shanshan Huang,† and Jun Lin*,† State Key Laboratory of Rare Earth Resource Utilization and State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, People’s Republic of China ReceiVed: March 3, 2010; ReVised Manuscript ReceiVed: April 13, 2010
Printed electronics is expected to be used for fabricating the next-generation displays. However, this technique is still in the laboratory scale and mainly limited to organic luminescent materials and inorganic quantum dots. In this article, a new attempt was made by combining the Pechini-type sol-gel process and inkjet printing for patterning an inorganic YVO4:Eu3+ thin film phosphor. The mixed solution of metal salts precursors, citric acid, and poly(ethylene glycol) was directly used as ink to deposit patterns on ITO-coated glass substrate. After calcination at 600 °C in air, the YVO4:Eu3+ patterns in micrometer-scale were formed on the substrates, and the photoluminescence (PL) and cathodoluminescence (CL) spectra were employed to characterize the obtained samples. A dominating red emission coming from 5D0-7F2 transition of Eu3+ was observed under excitation of UV light or electronic beam. These results demonstrate that the Pechini-type sol-gel process has good compatibility with the inkjet printing technique and has the potential to be used for fabricating the next-generation Field Emission Display (FED) devices. 1. Introduction Patterning phosphor materials to form a pixel matrix on screen is an essential and important technique for the fabrication of display devices. Full-color displays are generally needed to deposit the three color points (red-green-blue) on the desired regions to make up pixels. An accurate patterning technology for phosphor screen has paramount effect on the resolution of display devices. Some conventional methods, such as screen printing, vacuum deposition, electro-deposition, and photolithographic patterning technologies, have been used in current flat panel displays (FPDs) device fabrication.1 Although these technologies are mature and scalable for device fabrication in the microelectronics industry, there still exist a large number of shortcomings in terms of requiring expensive equipment, complex layout, and excessive loss of expensive phosphor materials during the fabrication process. Recently, inkjet printing has attracted substantial interest as a pathway to make display devices, in which the material deposition and patterning can be performed within a single step by a fully digital driven process.2–4 This direct-writing technique has many advantages such as simple, fast, large area, and low material consumption. There have been many reports for the applications of inkjet printing on the fabrication of polymer light-emitting diodes (PLED).5–12 The deposition of light-emitting polymers as pixels or conducting polymer PEDOT:PSS as the hole transportation layer can be carried out by inkjet printing in the PLED fabrication process. The bottleneck of the inkjet printing technique in organic electronics is being exceeded and some prototypes of full-color organic light-emitting televisions have been demonstrated.9,13 The quantum dots are also considered as excellent candidates for the inkjet printing route in fabricating a display device due to their good dispersibility in solvent and the size tunable light emission.14–16 Besides, an attempt has been * To whom correspondence should be addressed. E-mail:
[email protected]. Phone: +86-431-85262031(O). Fax: +86-431-85698041. † State Key Laboratory of Rare Earth Resource Utilization. ‡ State Key Laboratory of Polymer Physics and Chemistry.
made to pattern inorganic phosphor material for the applications of a plasma display panel (PDP).17 Field emission display (FED), also called a thin cathode ray tube (CRT) device, is perceived to be a strong candidate for FPDs applications, owing to its advantages of low power, high brightness, broad viewing angle, less smearing of fast moving video images, and tolerant to greater temperature ranges than other display types.18,19 Identically, the phosphor materials need to be patterned on an anode screen to form pixels in response to the electron bombardment coming from the tips matrix on the cathode. However, to the best of our knowledge, there is no report on patterning phosphor material via the inkjet printing route for FED exploration. Conventional phosphor materials are usually prepared via solid-state reaction. The high-temperature solid-state route produces large aggregates on the order of micrometers that must be milled to obtain the finer particles.20,21 The micrometer-scale particles combining with the conventional patterning methods (such as screen printing) will result in a very thick film. Unfortunately, the excitation depth of the electronic beam in phosphors is limited under the FED working condition because of the low voltage (
