Torres Ziegenbein Christian, Fröbel Sascha, Glöß Maria, Nobuyasu Roberto S, Data Przemyslaw, Monkman Andrew, Gilch Peter
Institut für Physikalische Chemie, Heinrich-Heine-Universität Düsseldorf, Universitätstr. 1, 40225, Düsseldorf, Germany.
Current address: Department of Chemistry, The Ohio State University, 100 West 18th Avenue, Columbus, OH, 43210, USA.
Chemphyschem. 2017 Sep 6;18(17):2314-2317. doi: 10.1002/cphc.201700683. Epub 2017 Jul 20.
The efficiency of organic light-emitting diodes crucially depends on triplet harvesters. These accept energy from triplet correlated electron hole pairs and convert it into light. Here, experimental evidence is given that simple aromatic carbonyls, such as thioxanthone, could serve this purpose. In these compounds, the emissive ππ* excitation may rapidly equilibrate with an upper triplet state ( nπ*). This equilibrium may persist for nanoseconds. Population of the nπ* state via energy transfer from an electron hole pair should result in fluorescence emission and thereby triplet harvesting. To demonstrate the effect, solutions of 1,4-dichlorobenzene (triplet sensitizer) and thioxanthone (harvester) were excited at 266 nm with a nanosecond laser. The emission decay reveals a 100 ns decay absent in the thioxanthone only sample. This matches predictions for an energy transfer limited by diffusion and gives clear evidence that thioxanthone can convert triplet excitations into light.
有机发光二极管的效率关键取决于三重态捕光剂。这些捕光剂从三重态相关的电子空穴对接收能量并将其转化为光。在此，有实验证据表明，简单的芳香羰基化合物，如噻吨酮，可起到此作用。在这些化合物中，发光的ππ激发态可能会与较高的三重态（nπ）迅速达到平衡。这种平衡可能会持续纳秒级。通过从电子空穴对进行能量转移使nπ*态发生粒子数增加，应会导致荧光发射，从而实现三重态捕光。为证明这种效应，用纳秒激光在266 nm波长下激发1,4 - 二氯苯（三重态敏化剂）和噻吨酮（捕光剂）的溶液。发射衰减显示，仅噻吨酮样品中不存在100 ns的衰减。这与受扩散限制的能量转移的预测相符，并清楚地证明噻吨酮可将三重态激发转化为光。
