Triazine and Thiophene-Containing Conjugated Polymer Network Emitter-Based Solution-Processable Stable Blue Organic LEDs

Abstract

The development of solution-processable fluorescent materials with blue electroluminescence has recently attracted considerable research interest for organic light-emitting diode (OLED) applications. Whereas, conjugated polymer frameworks (CPFs) or networks (CPNs) have attained tremendous research interest due to their vast potential in a variety of cutting-edge applications including photocatalysis, sensing, gas storage, energy storage, and so on. These framework/network materials without side chains or functional groups on their backbone are generally insoluble in common organic solvents and less solution-processable for electronic device applications. Herein, we have reported two triazine-based highly fluorescent and wide-band gap donor–acceptor conjugated polymer networks (CPNs) by coupling a 3-substituted thiophene (donor) unit with a triazine ring (acceptor) through a phenyl ring spacer. Two different side chains, alkyl and oligoethylene glycol, are rationally introduced into the 3-position of thiophene in the polymer network to make them solution-processable. Further physicochemical and optoelectronic characterizations of these emitters are performed in detail, and the effects of the side chain functionality and polarity on the above-mentioned properties are also thoroughly investigated. OLEDs based on these CPNs as emitters show a maximum external quantum efficiency of 2.3% with a maximum brightness of 2541 cd/m2 and a maximum current efficiency of 2.8 cd/A with blue emission [Commission Internationale de l’éclairage (CIE) coordinates of (0.17, 0.19)]. To the best of our knowledge, this may be the first example of conjugated polymer network material emitters being successfully designed, fabricated, and tested for solution-processable blue OLEDs. These results also demonstrate the high potential of the conjugated polymer network emitters for future blue or other color OLED applications.