Push–pull (D-π-A) dyes are explored for organic light-emitting electrochemical cells (LECs) taking advantages of their tunability in the intramolecular charge transfer (CT) through a π-bridge between donor and acceptor. These dyes present high thermal stability beyond 290 °C and fluorescence quantum yields (Φf), and simple thin film processability. The fluorene-based dyes with diphenylamine donor (DPF) show high tunability in electroluminescence wavelength up to 825 nm that corresponds to the most red-shifted metal-free LECs reported to date. The DPFs show high irradiance under a low working voltage in the presence of poly(9-vinylcarbazole) (PVK) and 2,5-bis(5-tert-butyl-benzoxazol-2-yl)thiophene (BBOT) hosts. As the CT distance of dyes is increased, Von of the LECs is decreased, since Φf and lifetime of dyes are higher. Furthermore, the smaller angle between the π-bridge and acceptor (AπA) of dye is critical to increase irradiance, for a closer dye–host proximity. Thus a DPF dye with the lowest AπA (dye I) affords the highest irradiance of 425 µW cm−2 (>220 Cd m−2) among the dyes in this study. Therefore push–pull dyes could provide a rational material design principle toward NIR emitting LECs.
All Science Journal Classification (ASJC) codes
- Materials Science(all)
- Condensed Matter Physics