A Study on Varying the Number of Fluorene Units in 2, 1, 3‐Benzothiadiazole‐Containing Oligomers and the Effect on OLED Performance and Stability

• Published in: ChemPhotoChem 2023-03, Vol.7 (3), p.n/a
• Main Authors: Lozano‐Hernández, Luis‐Abraham, Cameron, Joseph, Riggs, Christopher J., Reineke, Sebastian, Skabara, Peter J.
• Format: Article
• Language: English
• Subjects: conjugation; fluorene; organic light-emitting diodes; photophysics; semiconductors
• ISSN: 2367-0932; 2367-0932
• DOI: 10.1002/cptc.202200256

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. 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.