%0 Journal Article
%T Controlling Molecular Conformation for Highly Efficient and Stable Deep-Blue Copolymer Light-Emitting Diodes
%J -
%D 2018
%R https://doi.org/10.1021/acsami.8b00243
%X High Resolution Image Download MS PowerPoint Slide We report a novel approach to achieve deep-blue, high-efficiency, and long-lived solution-processed polymer light-emitting diodes (PLEDs) via a simple molecular level conformation change of an emissive conjugated polymer. We introduce rigid ¦Â-phase segments into a 95% fluorene¡ª5% arylamine copolymer emissive layer. The arylamine moieties at low density act as efficient exciton formation sites in PLEDs, whereas the conformational change alters the nature of the dominant luminescence from a broad, charge transfer like emission to a significantly blue-shifted and highly vibronically structured excitonic emission. As a consequence, we observe a significant improvement in the Commission International de L¡¯Eclairage (x, y) coordinates from (0.149, 0.175) to (0.145, 0.123) while maintaining high efficiency and improved stability. We achieve a peak luminous efficiency, ¦Ç = 3.60 cd/A, and a luminous power efficiency, ¦Çw = 2.44 lm/W, values that represent state-of-the-art performance for single copolymer deep-blue PLEDs. These values are 5-fold better than for otherwise-equivalent, ¦Â-phase poly(9,9-dioctylfluorene) PLEDs (0.70 cd/A and 0.38 lm/W). This report represents the first demonstration of the use of molecular conformation as a simple but effective method to control the optoelectronic properties of a fluorene copolymer; previous examples have been confined to homopolymers
%U https://pubs.acs.org/doi/10.1021/acsami.8b00243