Baldo MA, Thompson ME, Forrest SR
Center for Photonics and Optoelectronic Materials, Department of Electrical Engineering and the Princeton Materials Institute, Princeton University, New Jersey 08544, USA.
Nature. 2000 Feb 17;403(6771):750-3. doi: 10.1038/35001541.
To obtain the maximum luminous efficiency from an organic material, it is necessary to harness both the spin-symmetric and anti-symmetric molecular excitations (bound electron-hole pairs, or excitons) that result from electrical pumping. This is possible if the material is phosphorescent, and high efficiencies have been observed in phosphorescent organic light-emitting devices. However, phosphorescence in organic molecules is rare at room temperature. The alternative radiative process of fluorescence is more common, but it is approximately 75% less efficient, due to the requirement of spin-symmetry conservation. Here, we demonstrate that this deficiency can be overcome by using a phosphorescent sensitizer to excite a fluorescent dye. The mechanism for energetic coupling between phosphorescent and fluorescent molecular species is a long-range, non-radiative energy transfer: the internal efficiency of fluorescence can be as high as 100%. As an example, we use this approach to nearly quadruple the efficiency of a fluorescent red organic light-emitting device.
为了从有机材料中获得最大发光效率，有必要利用电泵浦产生的自旋对称和反对称分子激发（束缚电子 - 空穴对，即激子）。如果材料是磷光的，这是可行的，并且在磷光有机发光器件中已经观察到了高效率。然而，有机分子中的磷光在室温下很少见。荧光这种替代辐射过程更为常见，但由于需要自旋对称性守恒，其效率大约低75%。在这里，我们证明可以通过使用磷光敏化剂来激发荧光染料来克服这一不足。磷光和荧光分子物种之间的能量耦合机制是一种远程非辐射能量转移：荧光的内效率可以高达100%。例如，我们使用这种方法使荧光红色有机发光器件的效率几乎提高了四倍。
