Drastic Reduction in the Band gap – A Novel Material for Plastic Electronics

Abstract

The flexi glass PMMA has more research importance because of its low cost, good tensile strength, high transparency, low glass transition temperature, enough thermal stability and good insulation property with a band gap of about 4.6eV. Its application can be extended to the field of plastic electronics by reducing its optical band gap by using the proper dopants. In the present work, we have reduced this band gap drastically by doping it with a light emitting polymer (LEP) MDMO-PPV. The PMMA samples doped with different weight percentages of MDMO-PPV are prepared in chloroform as the solvent and characterized by UV-Visible spectrometer and Impedance analyzer. Optical band gap of the doped samples are calculated using Tauc’s plot. Pure PMMA has absorption in UV region whereas LEP doped PMMA has the absorption maximum in the visible region at about 600nm. The doped samples have the maximum onset wavelength of 630nm and the least energy gap of 1.96eV. There is a drastic reduction in the band gap of PMMA by more than 2.64eV.. The impedance analyzer studies confirm the increase in dielectric constant with increase in doping concentrations, which is the indication of presence of electrode polarization and formation of the space charge effects confirming non-Debye dependence. Dielectric loss increases with increase in doping level and decreases with increase in frequency. The increase in dielectric loss is due to the increase in the number of free ions. It is observed that the ac conductivity increases with increase in LEP doping. Such band gap tuned polymer films are the promising materials for electro-optics and nano-electronic devices. These new materials can be used in the construction of Transparent Electrodes, LEDs, OPVs, OFETs etc. The device construction using these new films is our work under progress