以LiF修饰阴极的有机电致发光器件性能的提高

提出了用一种无机半导体的模型来计算有机电致发光器件(OELDs)的J-V特性.通过在金属/有机物界面插入薄LiF层,由此引入的偶极子能极大地降低了电子的注入势垒和OELDs的开启电压.从而,载流子的注入得到了平衡,OELDs的性能得到了较大提高.经过数值计算,发现LiF插入层有一个约为1.5~5.0nm的最优厚度.LiF层太厚或太薄都会提高器件的开启电压、降低器件的性能.结果表明:这一模型可以用来解释OELD通过LiF修饰阴极后性能的提高.     

Energy transfer probability in organic electrophosphorescence device with dopant

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.     

金属/有机半导体界面偶极层的研究

利用金属/无机半导体界面模型对金属/有机半导体界面偶极层进行了数值研究.讨论了界面处金属/有机半导体原子间距与化学键密度对界面偶极能的影响;分析了界面层电场强度随化学键密度变化的原因;对界面偶极能与金属功函数之间的关系给出了合理的解释.