Efficient Single-Layer White Light-Emitting Devices Based on Silole-Containing Polymers

Efficient white-light-emitting polymers were developed through the incorporation of narrow-bandgap green-emitting and red-emitting siloles moieties into the blue-emitting fluorene and carbazole copolymers backbone. By carefully controlling the concentrations of the green- and red-emitting species in the resulting copolymers, a white-light emission was achieved due to the simultaneous emission from all three colors. EL devices based on the copolymers exhibited luminance efficiencies of 4.87 cd/A with color coordinates of (0.30, 0.31) that was very close to the ideal CIE chromaticity coordinates for pure white light of (0.33, 0.33). After thermal treatment under 160 degrees C, the devices showed the best luminous properties with external quantum yield of 3.39%, L-ELmax of 6.78 cd/A and color coordinate of (0.29, 0.30). Furthermore, the color coordinates remained almost unchanged over the range of operating potentials. The main operating process involve in the white electroluminescent process can be attributed to the direct charge trapping on the narrow band gap units and partial energy transfer from the blue-emitting segments to the green-and red-emitting siloles moieties.