ELECTROLUMINESCENCE AND PHOTOLUMINESCENCE EFFICIENCY OF POLY(P-PHENYLENEVINYLENE) DERIVATIVES

Alkoxy, alkyl, and cyano derivatives of poly(p-phenylenevinylene) [PPV] are used as the emissive layers in light-emitting diodes [LEDs] to obtain luminescence from red to blue. We present the luminescence efficiency for these soluble PPV derivatives, comparing the photoluminescence [PL] yields with the electroluminescence [EL] yields. PL efficiency increases with the fraction of non-conjugated units. EL efficiency depends not only on the radiative recombination efficiency of the emitting material but also on carrier transport to and within the material. Efforts to improve the efficiency and long term stability of these polymer LEDs are challenged by efficient and balanced carrier injection.