Saturated red light emitting polymers and devices

A series of saturated red emission copolymers, polyfluorene copolymers (PFO-DBT), were synthesized and characterized. The saturated red EL emission from the copolymer peaking at about 677 nm and electroluminescence (EL) efficiency of 1.4% based on simple device structure of ITO/PEDOT/PFO-DBT/Ba/Al, were achieved. The operation mechanism of the device was discussed and it was found that hole carrier injection is the major obstacle for improving EL efficiency and EL stability. To overcome such problem, we utilized MEH-PPV which has low HOMO level blended with the PFO-DBT copolymer to improve EL efficiency to 1.7%. Simultaneously, the EL emission lifetime of the device with PFO-DBT:MEH-PPV (50:50) blended polymer extended to 2000hrs. Monochrome passive red emission displays with the blended polymer were fabricated, and exhibited excellent pictures.