A polymer light-emitting electrochemical cell(LEC)offers an alternative approach to achieving electroluminescence (EL) from conjugated polymers. Different from a polymer light-emitting diode(PLED)

the emitting layer of LEC contains ionic conductor such as poly(ethylene oxide) (PEO) mixed with lithium salt. In these solid-state LECs

the conjugated polymers are p-doped on the anode side and n-doped on the cathode side and a light-emitting p-n junction is formed between the p-doped and n-doped regions. The LEC was shown to operate in both forward and reverse bias

effectively independent of the electrode workfunction. Compared with PLED

LEC has the advantages of low turn on voltage and high quantum efficiency of its electroluminescence. The luminescence of LEC based on emitting material poly[2-methoxy-5-(2-ethylhexyloxy)-1

4-phenylenevinylene](MEH-PPV) doped with red dye 4-dicyanomethylene-2-(tert-buty1)-6-methyl-4H-pyran(DCJTB) has been researched. The EL peak wavelength of LEC devices depends on the luminescent materials of LEC. Usually OLEDs changed emission wavelength by doped organic dye into host materials

but this method in LEC was not reported. Doping organic dye into the luminescent materials of LEC may change the emission wavelength of device and fabricate LECs with various emission wavelengths

even the white emitting LECs.Red dye DCJTB was doped into MEH-PPV then a LEC device with a sandwich structure of ITO/MEH-PPV+PEO+LiCF

3

SO

3

+DCJTB/Al is fabricated. EL peak wavelength of the LEC devices ranges from 570 nm to 650 nm continuously

depending on the doping concentration of DCJTB. In the photoluminescence(PL) spectra excited with the excitation wavelength of MEH-PPV

it is observed that the emission from MEH-PPV decrease and DCJTB increase with the rise of the doped DCJTB mass concentration. This indicates that energy transfer occur from MEH-PPV to DCJTB. The redshift of DCJTB’s emission caused by increasing its concentration is another factor for the phenomena.