Computational and spectroscopic investigation of the anomalous fluorescence of two benzothiadiazole derivatives. The originally assigned anti-Kasha mechanism could not be confirmed, but instead separate emission from a protonated form is s...
A Study on Varying the Number of Fluorene Units in 2, 1, 3‐Benzothiadiazole‐Containing Oligomers and the Effect on OLED Performance and Stability
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Different benzothiadiazole-containing oligomers are employed as emissive materials in organic light-emitting diodes (OLEDs). The materials differ by the number of fluorenes in the conjugated backbone, which influences the optical properties, OLED performance and lifetime.
Solution-processing has the potential to reduce the cost and energy requirements in the fabrication of organic light-emitting diode (OLED) devices. In non-doped emissive layers, polymers are commonly used but often suffer from batch-to-batch variation. Oligomers, which have precise molecular structures, avoid this problem but maintain the favourable film-forming properties that polymers possess. We present three benzothiadiazole-containing fluorene-based oligomers, BT-F32 , BT-F42 and BT-F52 , which have terfluorene, quaterfluorene and pentafluorene arms, respectively, attached to a benzothiadiazole core. The materials show very high photoluminescence quantum yields, with BT-F42 exhibiting the highest PLQY of 0.96 in the thin film. Although there is little change in the electroluminescence spectra, the oligomer size influences device performance. BT-F32 had an external quantum efficiency of 1.9 % and high luminance whilst BT-F42 reached an external quantum efficiency of 2.3 %. Furthermore, the stability of the OLED devices was evaluated and showed that the device lifetime decays with increasing molecular length.Zum Volltext
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