Effect of Different Sized Multi Walled Carbon Nanotubes on the Barrier Potential and Trap Concentration of Malachite Green Dye Based Organic Device

Abstract Present work shows effect of 8 nm diameter and 30 nm diameter multi walled carbon nanotubes (MWCNT) on the barrier potential and trap concentration of Malachite Green (MG) dye based organic device. MWCNTs are basically a bundle of concentric single-walled carbon nanotubes with different diameters. In this work, ITO coated glass substrate and aluminium have been used as front electrode and back electrode respectively and the spin coating method is used to prepare the MG dye based organic device. It has been observed that both barrier potential and trap concentration are in correlation. Estimation of both these parameters has been done from current-voltage characteristics of the device to estimate the trap energy and the barrier potential of the device. Device turn-on voltage or the transition voltage is also calculated by using current-voltage characteristics. In presence of 8 nm diameter MWCNT, the transition voltage is reduced from 3.9 V to 2.37 V, the barrier potential is lowered to 0.97 eV from 1.12 eV and the trap energy is lowered to 0.028 eV from 0.046 eV whereas incorporation of 30 nm diameter MWCNT shows reduction of transition voltage from 3.9 V to 2.71 V and a reduction of barrier potential and trap concentration from 1.12 eV to 1.03 eV and from 0.046 eV to 0.035 eV respectively. Presence of both 8 nm diameter and 30 nm diameter MWCNT lowers trap energy approximately to 39% and 24% respectively and lowers barrier potential approximately to 13% and 8% respectively. Estimation of barrier potential is also done by Norde method which shows lowering of the value from 0.88 eV to 0.79 eV and from 0.88 eV to 0.84 eV in presence of both 8 nm and 30 nm diameter multi walled carbon nanotubes respectively. Calculation of barrier potential from both the I-V characteristics and Norde method are in unison with each other. Indication of enhancement of charge flow in the device can be ascribed to the truncated values of barrier potential and trap energy.