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

Abstract

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-F3 2 , BT-F4 2 and BT-F5 2 , which have terfluorene, quaterfluorene and pentafluorene arms, respectively, attached to a benzothiadiazole core. The materials show very high photoluminescence quantum yields, with BT-F4 2 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-F3 2 had an external quantum efficiency of 1.9 % and high luminance whilst BT-F4 2 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.

Recent Advances in Monocomponent Visible Light Photoinitiating Systems Based on Sulfonium Salts

“…Different strategies were developed to redshift the absorption of the sulfonium salts, and an efficient strategy was proposed by using fluorene as a π-conjugated spacer [288]. Fluorene is an excellent electron-donating group that was notably used for the design of chromophores for solar cells [289][290][291][292][293][294][295][296][297][298][299], light emitters for OLEDs [300][301][302][303][304][305][306] and charge transport materials for OFETs [307][308][309][310][311][312][313][314][315] and as fluorescent probes [316][317][318][319][320][321][322][323]. The fluorene scaffold was notably used by Yagci and coworkers to design thioxanthone exhibiting a high molar extinction coefficient and a redshifted absorption compared with PI-PAG [324].…”

Helicene Appended Benzothiadiazoles as Chiral Emitters

“…The strongly emitting 2,1,3-benzothiadiazole (BTD) unit [1,2] has been extensively used over the years in the field of organic electronics, in the composition of materials for organic and dye sensitized solar cells, [3][4][5][6][7][8] organic light-emitting diodes, [9][10][11][12][13] organic field-effect transistors, [14][15][16][17] but also as fluorescent probes [18] or polymeric thermometers. [19] Thanks to its electron acceptor character, [20] BTD has been used as well in donoracceptor systems, [21][22][23][24] while the presence of sp 2 nitrogen atoms in the five-member thiadiazole ring makes it a valuable coordinating unit in an increasing number of functional ligands and derived metal complexes.…”