Highly efficient non-doped blue organic light-emitting diodes based on fluorene derivatives with high thermal stability

A new series of blue-light-emitting fluorene derivatives have been synthesized and characterized. The fluorene derivatives have high fluorescence yields, good thermal stability, and high glass-transition temperatures in the range 145-193 degrees C. Organic light-emitting diodes (OLEDs) fabricated using the fluorene derivatives as the host emitter show high efficiency (up to 5.3 cd A(-1) and 3.0 1m W-1) and bright blue-light emission (Commission Internationale de L'Eclairage (CIE) coordinates of x=0.16, y = 0.22). The performance of the non-doped fluorene-based devices is among the best fluorescent blue-light-emitting OLEDs. The good performance of the present blue OLEDs is considered to derive from: 1) appropriate energy levels of the fluorene derivatives for good carrier injection; 2) good carrier-transporting properties; and 3) high fluorescence efficiency of the fluorene derivatives. These merits are discussed in terms of the molecular structures.