Efficient color tuning (blue, red-orange, white) of light emitting diodes by excitation energy transfer

We present a color tuning technique allowing to control the emission colors of polymer light emitting diodes (PLEDs), which is of considerable interest for flat panel display applications. The emission color variation of the PLED from blue to red-orange is achieved by blending small amounts of a red light emitting guest polymer with the active PLED layer consisting of a blue emitting laddertype poly (paraphenylene) (LPPP). Using this new technique we realized highly efficient stable single layer PLEDs emitting different colors including white light emission. Besides the color tuning, which is established by an efficient excitation energy transfer (EET) and charge transfer from the host, m-LPPP, to the guest polymer, a significant increase of the photoluminescence (PL) and the electroluminescence (EL) quantum efficiency is observed. (C) 1998 Elsevier Science B.V.