J. Phys. Chem. C 2009, 113, 9911–9915
9911
Bright Red Upconversion Luminescence of Thulium Ion-Doped GeS2-In2S3-CsI Glasses Yinsheng Xu,† Danping Chen,*,‡ Qiang Zhang,‡,§ Huidan Zeng,† Ce Shen,† Jean-luc Adam, Xianghua Zhang,| and Guorong Chen*,† Key Laboratory for Ultrafine Materials of Ministry of Education, School of Materials Science and Engineering, East China UniVersity of Science and Technology, Shanghai 200237, China, Key Laboratory of Material Science and Technology for High Power Lasers, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800, China, Graduate School of the Chinese Academy of Sciences, Beijing 100039, China, and Laboratoire des Verres et Ce´ramiques, UMR-CNRS 6226, Sciences chimiques de Rennes, UniVersite´ de Rennes 1, Rennes, 35042, France ReceiVed: February 5, 2009; ReVised Manuscript ReceiVed: April 27, 2009
In this paper, we report a novel phenomenon in GeS2-In2S3-CsI chalcohalide glasses doped with Tm3+ ions. Under irradiation with an 808 nm laser diode, a bright red emission centered at 700 nm is observed for the first time. By codoping with different concentration of Er3+ ions, emission can be tuned from monochromatic red to green. The Er3+ ions codopant and higher concentration of Tm3+ ions are favoring the 700 nm red emission. Meanwhile, the indium (In) contents plays a significant role on the enhanced upconversion and near-IR emissions. These observations are interesting and may enable the device based on the chalcohalide glass to meet the specific color demands, which have potential applications in the fields of optical and solid state lasers. 1. Introduction The study of upconversion (UC) materials has greatly grown recently owning to their applications in solid-state lasers, optical fiber based telecommunications, illumination, white lightemitting diodes (WLED), flat panel displays, and biological labeling, and their ability to increase conversion efficiency in photovoltaic cells.1-15 UC, i.e., photoexcitation at a long wavelength followed by luminescence at a shorter wavelength, is typically observed in compounds containing rare earth (RE) ions. Several UC mechanisms are well established in 4f systems. Common to all of them is the existence of long-lived intermediate states, which act as a storage reservoir for the pump energy. Subsequent emission from higher excited states can be induced radiatively by excited state absorption (ESA) or nonradiatively by energy-transfer upconversion (ETU).1 The generation of visible UC fluorescence is a multiphoton process, which can easily be realized by excitation with a compact and cost-effective continuous wave NIR diode laser. Many RE ions have been reported for their efficient UC luminescence. Among them, the Tm3+ and Er3+ ions can efficiently emit photons in the blue, green, and red regions of the spectrum and have the ability to convert IR light to visible. The tunable red/green/blue (RGB) color can be obtained by different ratios of Er3+/Tm3+.8 Upon that, much attention has been paid to the study of Er3+/Tm3+ ions codoped materials. However, the red emission of RE ions is always located at 660 nm, which is not the standard red (700 nm) emission of RGB color. To date, there have been a number of reports in the literature about UC luminescence materials. To the best of our knowledge, among the reported UC materials, chalcogenide glass is one of * To whom correspondence should be addressed. Phone/fax: +86 21 64253395. E-mail:
[email protected] (G.C.) and
[email protected] (D.C.). † East China University of Science and Technology. ‡ Chinese Academy of Sciences. § Graduate School of the Chinese Academy of Sciences. | Laboratoire des Verres et Ce´ramiques, UMR-CNRS6226.
the most efficient UC host materials for visible UC fluorescence. Most of these studies about chalcogenide glass, however, have been performed in GeS2-Ga2S3 (or La2S3, As2S3)-based materials. Moreover, to obtain higher UC efficiency, researchers often introduced alkali halides, which can enhance the RE emission properties and have no significant reduction of the IR transparency and RE solubility in these sulfur-halide (viz. chalcohalide) glasses.2 Furthermore, the alkali halides addition shifts the visible transparency toward shorter wavelengths.2,16 This extended transmission in the visible region is advantageous for effective pumping of active ions in the visible and may also allow efficient UC processes. In recent years, some new glasses based on indium (In) have been reported for its glass-forming ability and nonlinearity.17,18 Due to the presence of relatively heavy atoms (In), this glass has a low maximum phonon energy (MPE) of
