Liquid-crystalline Triplet Emitters of Iridium(III)

平板显示器现在的销量超过了那些基于阴极射线管技术的显示器，到目前为止，其中最受欢迎的是液晶显示器。然而，OLED代表了一种具有竞争力的技术，其可以具有利基应用并且与印刷技术和机械柔性显示器非常兼容。有机LED材料（例如聚合物LED）从通过电荷注入在器件中产生的单重态发射，但是产生的三重态具有太长（即毫秒）而不能使用的寿命。由于产生的三重态是单重态的三倍，因此这些系统的效率没有优化。为了有用，三重态发射体需要短得多的寿命。这可以在含有重过渡元素的金属络合物中实现，其中有效的自旋-轨道耦合“规避”了三重态衰变的自旋禁止性质，允许从单重态和三重态发射。目前在器件中使用的金属络合物含有铱（III）（这些是红色发光组分）。如果将络合物制备为液晶衍生物，则可以实现三重态发光体应用的重大发展，因为这可以导致取向，从而导致偏振发射。白色偏振发射将通过消除对后偏振器的需要而大大提高液晶显示器的背光效率，从而大大减少吸收损耗。然而，液晶性与铱（III）络合物（八面体）的几何形状不容易相容。我们现在已经证明，这种不相容性可以得到解决，并且我们有了LC铱发射体的第一个例子。在这些系统的开发建议中，我们提出：-调整可用的液晶范围;-修改设计以允许随时调整发色团;-评估设备特性以向潜在的最终用户提供必要的数据。

Flat-panel displays now outsell those based on cathode ray tube technologies and by far the most popular of these are liquid crystal displays. However, OLEDs represent a competitive technology that can have niche applications and that are very compatible with printing technologies and mechanically flexible displays. Organic LED materials (e.g. polymers LEDs) emit from singlet states created in the device by charge injection, but the triplet states produced have lifetimes that are too long (i.e. milliseconds) to be useful. As three times as many triplet state are produced compared to singlet states, efficiency in these systems is not optimised. To be useful, triplet emitters need much shorter lifetimes. This can be accomplished in metal complexes containing heavy transition elements where efficient spin-orbit coupling 'circumvents' the spin-forbibben nature of triplet decay, allowing emission from singlet and triplet states. The metal complexes currently used in devices contain iridium(III) (these are the red emitting component).A significant development in the application of triplet emitters could be realised if the complexes were prepared as liquid crystalline derivatives, as this could lead to alignment and, therefore, polarised emission. White, polarised emission would greatly improve the efficiency of backlighting for liquid crystal displays by removing the need for the back polariser, reducing absorptive losses hugely. However, liquid crystallinity is not readily compatible with the geometries of the iridium(III) complexes (octahedral).We have now demonstrated that this incompatibility can be addressed and we have the first examples of LC iridium emitters. In the proposal for development of these systems we propose:-tuning of the available liquid crystal range;-modified design to allow ready tuning of the chromophore;-evaluation of device characteristics to provide essential data to potential end users.