4‐(dicyanomethylene)‐2‐methyl‐6‐(p‐dimethylaminostyryl)‐4H‐pyran (DCM)‐doping density dependence of luminescence spectra and white emission in polymer light‐emitting diodes

Abstract

Abstract We fabricated white polymer light‐emitting diodes (PLEDs), in which the active region is doped with a low‐weight molecule. The host polymer material is Poly(9,9‐didodecyl‐fluorenyl‐2,7‐yleneethylnylene) (PFO), while the guest luminescent low‐weight‐molecule is 4‐(Dicyanomethylene)‐2‐methyl‐6‐(p‐dimethylaminostyryl)‐4H‐pyran (DCM). The photoluminescence (PL) and electroluminescence (EL) spectra strongly depend on DCM‐doping‐density. However, the most suitable DCM‐doping‐densities for white emissions in PL and EL are slightly different. This discrepancy is caused by the difference in excitation efficiencies. The photo‐excitation system for PL measurement is better than the current injection for generating carriers efficiently. Thus, the realization of the white EL signal requires the larger DCM‐doping‐density than that of the white PL signal. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)