Effect of back electrode on trap energy and interfacial barrier height of crystal violet dye-based organic device

Abstract

In this work, we have studied the effect of aluminium-coated mylar (Al–M) sheet-based back electrode and aluminium (Al)-coated back electrode on trap energy ($E_{\mathrm {t}})$ and barrier height ($\phi _{\mathrm {b}})$ of crystal violet (CV) dye-based organic device. Two devices have been prepared using two different back electrodes. In both the devices, ITO-coated glass is used as front electrode. Both the organic devices have been prepared by using spin-coating techniques. We have measured the steady state current–voltage (I–V) characteristics of these devices to estimate the trap energy ($E_{\mathrm {t}})$ and barrier height ($\phi _{\mathrm {b}})$ of the devices. Because of the insertion of a reflecting back electrode, the charge carriers are confined in the active layer, which reduces the $E_{\mathrm {t}}$ from 0.044 to 0.034 eV and $\phi _{\mathrm {b}}$ is reduced from 0.80 to 0.77 eV. The barrier height is also estimated by using another alternative method, which is known as Norde method. By using Norde method, $\phi _{\mathrm {b}}$ is estimated, which reduces from 0.83 to 0.79 eV in the presence of reflecting back electrode. Both the methods show good consistency with each other. The reductions of these parameters indicate the enhancement of charge injection through the metal-organic dye interface. With the use of polished back electrode in the CV dye-based organic device, it is possible to modify the barrier height and trap energy and thereby modifies the conductivity.