A new interface engineering method is demonstrated for the preparation of an efficient white organic light-emitting diode (WOLED) by embedding an ultrathin layer of the novel ambipolar red emissive compound 4,4-difluoro-2,6-di(4-hexylthiopen-2-yl)-1,3,5,7,8-pentamethyl-4-bora-3a,4a-diaza-s-indacene (bThBODIPY) in the exciplex formation region. The compound shows a hole and electron mobility of 3.3 × 10^–4 and 2 × 10^–4 cm² V^–1 s^–1, respectively, at electric fields higher than 5.3 × 10⁵ V cm^–1. The resulting WOLED exhibited a maximum luminance of 6579 cd m^–2 with CIE 1931 color coordinates (0.39; 0.35). The bThBODIPY dye is also demonstrated to be an effective laser dye for a cholesteric liquid crystal (ChLC) laser. New construction of the ChLC laser, by which a flat capillary with an optically isotropic dye solution is sandwiched between two dye-free ChLC cells, provides photonic lasing at a wavelength well matched with that of a dye-doped planar ChLC cell.

A new triaryl molecule based on a benzene–benzothiadiazole–benzene core has been applied in a WOLED device.

The bicarbazole derivative 4,4′-(9H,9′H-[3,3′-bicarbazole]-9,9′-diyl)bis(3-(trifluoromethyl)benzonitrile), denoted as pCNBCzoCF₃, was synthesized and tested for white OLED applications. pCNBCzoCF₃ demonstrated an extremely small value of the singlet–triplet energy gap that caused intensive thermally activated delayed fluorescence (TADF). In addition, this compound is able to form exciplex-type excited states at the interface with star-shaped 4,4′,4′′-tris[phenyl(m-tolyl)amino]triphenylamine (m-MTDATA). Combining the TADF emission of pCNBCzoCF₃ with the exciplex emission from the pCNBCzoCF₃/m-MTDATA interface, we fabricated a number of highly efficient “warm-white” OLEDs, the electroluminescence of which was close to candle emission. The best device demonstrated a very high brightness of 40 900 Cd m⁻² (at 15 V), current efficiency of 53.8 Cd A⁻¹ and power efficiency of 19.3 lm W⁻¹, while the external quantum efficiency reached 18.8%. The fabricated devices demonstrated high emission characteristics even for the standard test at 1000 Cd m⁻² (current efficiency of 46.2 Cd A⁻¹, power efficiency of 10.6 lm W⁻¹, EQE of 17.0%).