Energy transfer in a ternary system composed of Tb(DBM) 3 Phen, Eu(DBM) 3 Phen, and poly(N-vinylcarbazole)
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Xiaowu Yu, Wei Su, Zhoushun Zhang, Wenxuan Wu, Qing Yan, and Qijin Zhanga) Chinese Academy of Sciences, Key Laboratory of Soft Matter Chemistry, Department of Polymer Science and Engineering, University of Science and Technology of China, Key Laboratory of Optoelectronic Science and Technology, Anhui 230026, China (Received 8 March 2009; accepted 10 June 2009)
A ternary system composed of Tb(DBM)3Phen (TbDP), Eu(DBM)3Phen (EuDP), and poly(N-vinylcarbazole) (PVK) was prepared with good thermal stability and the photoluminescence (PL) was studied. By comparing their emissions, it was found that energy transfer exists from PVK to lanthanide complexes in the ternary system. It also was found that the lifetime of 5D0 of Eu3+ in the ternary system is longer than that of the binary system of EuDP and PVK, but the lifetime of 5D4 of Tb3+ in the ternary system is shorter than that of the binary system of TbDP and PVK, showing evidence of energy transfer from TbDP to EuDP. Temperature-dependent PL spectra of the ternary system from 9 to 300 K further showed there is a change in energy transfer efficiencies from Tb3+ ions to Eu3+ ions at different temperature ranges, which not only is more evidence of energy transfer but also can be used as a temperature detector or a thermal-sensitive probe of a optical fiber sensor. I. INTRODUCTION
In the past decade, lanthanide complexes have attracted great attention of many researchers because of their photonic applications, such as organic lightemitting diodes, optical fiber amplifiers, and so on.1–8 Lanthanide complexes have been used in organic photoluminescence (PL) devices for a long time because they have characters of high quantum efficiencies and sharp band emission.6,9,10 In applications, such as organic lightemitting diodes containing these low-molecular-weight lanthanide complexes, there are still some problems to be resolved, although such fluorescent dyes generally show impressive luminescence properties.11,12 These complexes usually exhibit poor carrier-transporting and film-forming abilities. Moreover, they decompose easily during vacuum vapor deposition, which is a common technique for fabricating organic electroluminescence devices.12,13 As a result, conventional lanthanide complexes show rather high PL efficiency but very low electroluminescence efficiency when they are incorporated into light-emitting diodes.14 This phenomenon severely impedes the practical application of lanthaa)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2009.0388 J. Mater. Res., Vol. 24, No. 10, Oct 2009
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nide complexes in such electroluminescence devices. To overcome these drawbacks, the lanthanide complexes are usually dispersed in polymer matrices, such as poly (N-vinylcarbazole) (PVK). On the other hand, organic electroluminescence devices using polymers dispersed with fluorescent dye have excellent heat stability and simple fabrication processes.12 To incorporate lanthanide ions into hydrophobic
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