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

Among the conjugate polymers, poly(3,4-ethylenedioxythiophene): poly (styrenesulfonate) (PEDOT:PSS) has been paid a great deal of attention for various application fields. The absorption intensity of the whole UV-visible range increases linearly, as the concentration of PEDOT: PSS increases. When a small amount of TiO2 nanoparticles are dispersed in the PEDOT: PSS solution, the absorption in 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 ratios of TiO2 nanoparticles in PEDOT:PSS were prepared. The TiO2/PEDOT:PSS solution was spin-coated onto the A1 electrode and thermally treated to remove water molecules and densify the film. These thermal processes generated nanocracks and nanoholes on the surface of the TiO2/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 heating processes. Schottky diodes were fabricated using four different concentrations of TiO2-PEDOT: PSS solution. The forward current increased nearly two orders of magnitude by doping approximately 1% of TiO2 nanoparticles in PEDOT: PSS. Increasing the TiO2 nanoparticles in the PEDOT: PSS matrix, the forward current was continuously enhanced. The enhancement of forward current is nearly four orders of magnitude with respect to the pristine PEDOT:PSS Schottky diode. The possible conduction mechanisms were examined by using various plotting and curve-fitting methods including a space-charge-limited conduction mechanism [Ln(J) versus Ln(V)], Schottky emission mechanism [Ln(J) versus E-1/2], and Poole-Frenkel emission mechanism [Ln(J/V) versus E-1/2]. The plot of Ln(J) versus Ln(V) shows a linear relationship, implying that the major conduction mechanism is SCLC. As the concentration of TiO2 increased, the conduction mechanism slightly detracted from the ideal SCLC mechanism.