The TiO2 nanoparticle effect on the performance of a conducting polymer Schottky diode

Abstract

Among the conjugate polymers, poly(3,4-ethylenedioxythiophene):poly (styrenesulfonate)(PEDOT:PSS) has been paid a great deal of attention for various applicationfields. The absorption intensity of the whole UV–visible range increases linearly,as the concentration of PEDOT:PSS increases. When a small amount ofTiO2 nanoparticles are dispersed in the PEDOT:PSS solution, the absorptionin the visible range normally increases, but the UV range absorption(TiO2 absorption area) is greatly depressed as the concentration of PEDOT:PSS increases. Various weight ratiosof TiO2 nanoparticles in PEDOT:PSS were prepared. TheTiO2/PEDOT:PSS solution was spin-coated onto the Al electrode and thermally treated to remove water molecules anddensify the film. These thermal processes generated nanocracks and nanoholes on the surface of theTiO2/PEDOT:PSS film. As the heating temperature increased, wider and longer nanocracks were generated.These nanocracks and nanoholes can be removed by subsequent coating and heatingprocesses. Schottky diodes were fabricated using four different concentrations ofTiO2–PEDOT:PSS solution. The forward current increased nearly two orders of magnitude by doping approximately 1%of TiO2 nanoparticles in PEDOT:PSS. Increasing theTiO2 nanoparticles in the PEDOT:PSS matrix, the forward current was continuouslyenhanced. The enhancement of forward current is nearly four orders ofmagnitude with respect to the pristine PEDOT:PSS Schottky diode. Thepossible conduction mechanisms were examined by using various plotting andcurve-fitting methods including a space-charge-limited conduction mechanism[Ln(J) versusLn(V)], Schottky emissionmechanism [Ln(J) versusE1/2], and Poole–Frenkelemission mechanism [Ln(J/V) versus E1/2]. Theplot of Ln(J)versus Ln(V) shows a linear relationship, implying that the major conduction mechanism is SCLC. As the concentrationof TiO2 increased, the conduction mechanism slightly detracted from the ideal SCLC mechanism.