Enhancing Seebeck Effects by Using Excited States in Organic Semiconducting Polymer MEH-PPV Based on Multilayer Electrode/Polymer/Electrode Thin-Film Structure

Abstract

This article reports the experimental studies on using photoexcitation-generated excited states as a new approach to increase Seebeck coefficient as well as electrical conductivity in an organic semiconducting polymer MEH-PPV (poly(2-methoxy-5-(2′-ethylhexyloxy)-p-phenylene vinylene) with multilayer electrode/polymer/electrode thin-film architecture. Our experimental results show that a photoexcitation can lead to a large Seebeck coefficient of 305 μV/K in the ITO/MEH-PPV/Au device under the light intensity of 16 mW/cm2. Simultaneously, the electrical conductivity is increased to 8.2 × 10–5 S/cm from the dark conductivity of 3.6 × 10–6 S/cm. Clearly, using excited states can lead to a simultaneous increase on Seebeck coefficient and electrical conductivity, as compared to opposite phenomenon induced by doping: increasing electrical conductivity but decreasing Seebeck coefficient. Our experimental studies suggest that excited states can increase both the entropy difference between high and low-temperature ...