Int. J. Adv. Sci. Eng. Vol.6 No.S2 23-27 (2020) 23 E-ISSN: 2349 5359; P-ISSN: 2454-9967 Sudipta Sen & Nabin Baran Manik International Journal of Advanced Science and Engineering www.mahendrapublications.com Study on the Effect of 8 nm Size Multi Walled Carbon Nanotubes (MWCNT) on the Barrier Height of Malachite Green (MG) Dye Based Organic Device Sudipta Sen * , Nabin Baran Manik Condensed Matter Physics Research Centre, Department of Physics, Jadavpur University, Kolkata - 700032, India. 1. INTRODUCTION In these days, organic/polymer materials are being widely investigated to develop different electronic and optoelectronic devices. Organic devices are more flexible, light weight, cost effective and can be easily fabricated over a large area. Despite these advantages, there are also certain limitations of organic devices. One of the major limitations is the high barrier height (ϕ b ) at metal-organic layer interface. Due to high interfacial barrier height, the charge injection from metal to organic layer is low which attributes to higher threshold voltage (Vth). There is not much study on the barrier height particularly at below threshold voltage (Vth) of organic devices at the metal-organic layer interface. Attempts need to be made to reduce the barrier height to improve the charge injection at the interface of metal-organic layer and thereby to reduce the threshold voltage. At the below threshold voltage regime, the charge injection process is strongly dependent on the barrier height at the metal- organic layer interface [1-2]. Barrier height at the metal- organic semiconductor interface is an important parameter for the injection of charge carriers at the low voltage or below threshold voltage regime. The process of charge injection at the interface of metal and organic material has a significant impact on the electrical properties of organic devices. To reduce the barrier height at the metal-organic layer interface, we have incorporated 8 nm MWCNT within the device. MWCNT reduces the interfacial barrier height and the threshold voltage at the metal-organic semiconductor interface. Reduction of interfacial barrier height will lead to better injection of charges at the interface and thus will provide better conductivity [3]. Generally, the injection barrier height at the metal to organic interface is commonly described by the metal to semiconductor contact. Injection- limited current flow generally occurs at below threshold voltage region. Injection current generally consists of thermionic-injection current and field-induced tunnelling current. At the low voltage region, field induced tunnelling current is so small that it can be neglected. For this reason, Richardson – Schottky (RS) model of thermionic emission is used to characterize the device at low voltage region [4]. 2. MATERIALS AND SAMPLE PREPARATION MG dye and non functionalized MWCNT are purchased from Finer Chemicals, Ahmedabad and Sisco Research Laboratories, India respectively. MG dye is a triarylmethane dye. PolyMethyl Methacrylate (PMMA) is procured from Merck Specialties Pvt. Ltd, Mumbai. Here PMMA acts as an inert binder [5]. To fabricate the organic device, Indium Tin Oxide (ITO) coated glass is used as the front electrode and Aluminium (Al) is used as the back electrode. Fig. 1 (a) and Fig. 1 (b) show the structures of MG dye and MWCNT respectively. 10 ml of double distilled water is taken in a clean test tube and in it 1g of PMMA is added to prepare the MG dye solution. To get a clear solution, the mixture is stirred with a magnetic stirrer for 30 min. In this solution, 1 mg of MG dye is added and stirred for 15 min. This solution is then divided into two parts in two pre-cleaned test tubes. In the test-tube MWCNT of size 8 nm are added respectively and stirred for 2 hours to get a homogeneous solution of dye and ABSTRACT: In this paper, we have studied the effect of 8 nm sized multi walled carbon nanotubes (MWCNT) on the barrier height (ϕ b ) of ITO coated glass/Malachite Green (MG) dye /Aluminium (Al) based organic device. Presence of 8 nm MWCNT reduces the metal-organic interfacial barrier height as it enhances the charge separation and relaxation process. We have used ITO coated glass as front electrode and aluminium as back electrode to form the organic device. This organic device has been prepared with and without MWCNT by using spin coating technique. We have measured the steady state current-voltage (I-V) characteristics of the device to estimate the Vth and barrier height (ϕ b ) of the device. In the presence of 8 nm MWCNT, Vth is reduced from 3.9 V to 2.37 V and ϕ b is reduced from 1.12 eV to 0.97 eV. Reduction of the threshold voltage and barrier height in the presence of MWCNT indicates the enhancement of charge injection through the metal- organic dye interface. By suitable doping or addition of MWCNT within the MG dye it is possible to modify the barrier height and thereby to control the threshold voltage and the conductivity. KEYWORDS: Malachite Green Dye; Threshold Voltage; Barrier Height; 8 nm MWCNT https://doi.org/10.29294/IJASE.6.S2.2020.23-27 © 2020 Mahendrapublications.com, All rights reserved *Corresponding Author: sagnike000@gmail.com Received: 20.10.2019 Accepted: 18.12.2019 Published on: 27.01.2020