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%).

In this research, conducting polymer – polypyrrole (Ppy), was electrochemically polymerized on the indium tin oxide coated glass (glass/ITO) electrode. The adhesion of Ppy on the surface of ITO was improved by modification with triethoxymethylsilane (TEMS). Potential cycling was applied for electrochemical deposition of Ppy layer and cyclic voltammograms were recorded during the deposition to monitor polymerization process. Cyclic voltammetry and the potential pulse sequence (PPS)-based chronoamperometry methods complemented the registration of absorbance spectra of glass/ITO_(TEMS)/Ppy at various pH and different concentrations of CO₂. The applicability of glass/ITO_(TEMS)/Ppy electrode in the design of electrochromic sensor sensitive toward CO₂ has been evaluated. Cyclic voltammetry based experiments at different potential sweep rates in presence and absence of CO₂ were performed in order to evaluate charge transfer phenomenon in glass/ITO_(TEMS)/Ppy structure.