Charge transport through conducting organic poly(2-methoxy-5- (2-ethylhexyloxy)-1, 4-phenylenevinylene)

Abstract

Current–voltage (J–V) characteristics of poly(2-methoxy-5- (2-ethyhexyloxy)-1, 4-phenylenevinylene)(MEH-PPV) have been studied in the hole-only devices ITO/PEDOT : PSS/MEH-PPV/Au, as a function of temperature from 300 to 98 K. Hole conduction in MEH-PPV has been well explained by an exponential trap-controlled drift model. In a considerable range of applied voltages, current obeys the power law J ∝ Vl+1, where l = Tc/T and Tc is the characteristic temperature of the exponential trap distribution. Assuming the effective density of states Nν = 2.7 × 1018 cm−3, the holes trap density (Hb) and characteristic temperature (Tc) have been calculated to be 1 × 1018 cm−3 and 550 K, respectively. As the voltage further increases current deviates and becomes smaller than J ∝ Vl+1. At low temperatures and sufficiently high-applied voltages, current follows the V2 law. At higher temperatures slopes less than 2 of the log J–log V plots have been observed. The possible reasons for this behaviour are mentioned.