Novel cross-linked deep-blue fluorene-based emitters for full-solution-processed organic light-emitting diodes†

The development of full-solution-processed organic light-emitting diodes (OLEDs) holds profound implications for low-cost, large-area, wearable organic electronic devices. Efficient blue emissions with high color purity and stability are essential to full-color displays. In this work, three thermally cross-linkable deep-blue emitters, V-MFCz, V-HFCz, and V-SAFCz, were designed and synthesized. Systematic studies demonstrated that solution-processed films derived from the three molecules exhibited excellent photophysical properties, thermal stability, and solvent resistance. The full-solution-processed OLEDs based on V-MFCz, V-HFCz, and V-SAFCz exhibited deep-blue emissions with peaks at 440, 443, and 444 nm, and the full widths at half-maximum (FWHM) of 43, 49, and 48 nm, respectively. The Commission Internationale de L’Eclairage (CIE) coordinates of the device based on V-MFCz were (0.16, 0.08), which are close to the NTSC standard blue emission of (0.14, 0.08). By tuning the molecular structure, V-SAFCz achieved the best device performance with maximum current efficiency (CE_max), maximum power efficiency (PE_max), and maximum external quantum efficiency (EQE_max) of 3.13 cd A⁻¹, 1.7 lm W⁻¹, and 1.91%, respectively. In this work, full-solution-processed non-doped deep-blue OLEDs were achieved, and the application of cross-linking strategies based on three primary colors (red, green, and blue) was expanded.