Reineke Sebastian, Baldo Marc A
Energy Frontier Research Center of Excitonics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA.
Sci Rep. 2014 Jan 21;4:3797. doi: 10.1038/srep03797.
Organic light-emitting devices and solar cells are devices that create, manipulate, and convert excited states in organic semiconductors. It is crucial to characterize these excited states, or excitons, to optimize device performance in applications like displays and solar energy harvesting. This is complicated if the excited state is a triplet because the electronic transition is 'dark' with a vanishing oscillator strength. As a consequence, triplet state spectroscopy must usually be performed at cryogenic temperatures to reduce competition from non-radiative rates. Here, we control non-radiative rates by engineering a solid-state host matrix containing the target molecule, allowing the observation of phosphorescence at room temperature and alleviating constraints of cryogenic experiments. We test these techniques on a wide range of materials with functionalities spanning multi-exciton generation (singlet exciton fission), organic light emitting device host materials, and thermally activated delayed fluorescence type emitters. Control of non-radiative modes in the matrix surrounding a target molecule may also have broader applications in light-emitting and photovoltaic devices.
有机发光器件和太阳能电池是在有机半导体中产生、操控和转换激发态的器件。表征这些激发态或激子对于优化诸如显示器和太阳能收集等应用中的器件性能至关重要。如果激发态是三重态，这会变得复杂，因为电子跃迁是“暗的”，振子强度消失。因此，三重态光谱通常必须在低温下进行，以减少来自非辐射速率的竞争。在这里，我们通过设计包含目标分子的固态主体基质来控制非辐射速率，从而能够在室温下观察磷光，并减轻低温实验的限制。我们在具有多种功能的广泛材料上测试了这些技术，这些功能包括多激子产生（单重态激子裂变）、有机发光器件主体材料以及热激活延迟荧光型发光体。控制目标分子周围基质中的非辐射模式在发光和光伏器件中可能也有更广泛的应用。
