Temperature Dependence of Electro- and Photo-Luminescence of a Silyl-Disubstituted PPV Derivative

Abstract

We have studied the temperature dependences of the current-voltage (I - V ) characteristics, the electroluminescence (EL), and the photoluminescence (PL) of light-emitting diodes fabricated with poly(2,5-bis(dimethyloctylsilyl)-1,4-phenylenevinylene) (BDMOS-PPV). The ITO/BDMOSPPV/ Al devices show green light emission under both forward and reverse biases. The I - V characteristics under both biases t the Fowler-Nordheim tunneling formula at high elds, and the current and the EL intensity under a constant bias are independent of temperature below about 270 K, indicating that the tunneling of charge carriers is an important injection process. The EL spectra under both biases are very similar to the PL spectra and are narrower compared than the optical absorption spectrum. These results and a red-shift of the transient PL spectra with time imply that excitons migrate towards longer conjugated segments prior to recombination.