Abstract Based on the energy transfer process from host to dopant in an organic electrophosphorescent (EP) device, the expression of energy transfer probability ($\eta )$ between the host (TPD) and guest (Ir(ppy)$_{3})$ EP systems was proposed. The results show that: (1) The rate of the triplet energy transfer ($K_{\rm HG}$ and $K_{\rm GH})$ increases exponentially with increasing donor-acceptor molecular distance ($R$), whereas decreases as the intermolecular distance ($R_{\rm HH})$ increases from 0.8 to 2.4 nm. Furthermore, $K_{\rm GH}$ changes more quickly than $K_{\rm HG.}$ (2) The energy transfer probability ($\eta )$ increases as $R$ reduces, and the $R_{\rm HH}$ changes can be safely neglected for $R<$0.9 nm. The situation changes for 0.9nm$ < R < 1.1$nm, $R_{\rm HH }$ ($<1$nm) plays an essential role when $\eta $ changes and increases with the latter. However, if $R > 1.1$nm, the transfer probability will be below zero. Here, the energy transfer principle may be less important, and the high electroluminescence (EL) quantum efficiency of phosphorescent system will be attributed to the direct electron-hole recombination in phosphorescent molecules. (3) The $\eta $ will increase when the Forster radius ($R_{0})$ increases or Gibb's energy decreases.
Received: 22 April 2005
Revised: 24 August 2005
Accepted manuscript online:
PACS:
78.60.Fi
(Electroluminescence)
Fund: Project supported by the Excellent Youth Foundation of Hu'nan Province (Grant No 03JJY1008), and by the Science Foundation for Post-doctorate of China (Grant No 2004035083).
Cite this article:
Dai Guo-Zhang (代国章), Li Hong-Jian (李宏建), Pan Yan-Zhi (潘艳芝), Dai Xiao-Yu (戴小玉), Xie Qiang (谢强) Energy transfer probability in organic electrophosphorescence device with dopant 2005 Chinese Physics 14 2590
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