High-color-quality white emission in AC-driven field-induced polymer electroluminescent devices

The high-color-quality white emission in an AC-driven field-induced electroluminescence (FIPEL) device consisting of a white emitting ter-polymer: poly(fluorene–benzothiadiazole–quinoline) PF–BT–QL combined with a red emitting dye: Bis(2-methyl-dibenzof,hquinoxaline)(acetylacetonate)iridium (III) Ir(MDQ)2(acac) was achieved. The wide EL emission effectively covered the visible spectral region at the concentration of 5% Ir(MDQ)2(acac) in PF–BT–QL and largely enriched the color rendering capability with a CIE (0.36, 0.38) close to the ideal equal-energy white (0.33, 0.33) and a CRI as high as 97.4, close to the blackbody curve characteristic and CCT between 3034 K and 5334 K which are required for high-quality white-light illumination. When further increasing the concentration of Ir(MDQ)2(acac) to 10%, leading to a more pure white with CIE (0.36, 0.37) and a CRI as high as 97.1. Surprisingly, the FIPEL devices containing 20% and 30% Ir(MDQ)2(acac) in PF–BT–QL still exhibit high-quality white emission with CIE (0.42, 0.37) and (0.32, 0.38) and CRI 93.9 and 88.9 at high electric field, respectively. To the best of our knowledge, there are no reports of two-component FIPELs with a CRI > 90, especially with such a high concentration of the phosphor dopant. We attribute this to the unique carrier injection characteristics of the AC-driven field induced device. This further suggests its great potential application in display and solid state lighting.