Triphenylamine-based donor–π–acceptor organic phosphors: synthesis, characterization and theoretical study
We have designed and synthesized donor (D) and acceptor (A) phosphors [D and A refer to the electron-donating and electron-withdrawing moieties, respectively] as yellow-emitting organic phosphors. The photophysical and electrochemical properties of the phosphors have been studied in detail. The UV-vis spectra of the organic phosphors show multiple absorption bands (UV to near UV region, due to π–π* transitions of the conjugated chains), and all the phosphors show yellowish-green/yellow (556, 576, 594 nm) emission with appropriate Commission Internationale de I'Eclairage (CIE) color coordinate values. In contrast, a bathochromic shift was observed in the solid-state emission spectra for the one donor–two acceptors and one donor–three acceptors due to the π–π interaction and aggregation induced emission. Electrochemical studies were carried out to find the HOMO, LUMO and band gap of the phosphors, and these were verified by density functional theory (DFT) calculations. By using time dependent-DFT (TD-DFT) calculations, singlet and triplet energy levels were also calculated. In addition, solvatochromism studies were also carried out and the results were interpreted using the Lippert–Mataga equation. White light can be realized from the currently synthesized organic yellow phosphors integrated with blue LEDs or blue fluorophores.