Reversible thermochromic effects in poly(phenylene vinylene)-based polymers

Abstract

We study the thermochromic response of poly [2-methoxy-5-(2 -ethylhexyloxy)-1,4-phenylenevinylene] (PPV) gel films. These films undergo a reversible, continuous color change from red to yellow in the practically relevant temperature range of 25–100°C. We show that the absorption and photoluminescence continuously decrease and blueshift along with an increase in both highest occupied molecular orbital and lowest unoccupied molecular orbital levels as the temperature is increased, and that this effect does not depend on glass transition temperature. Understanding the changes in this widely used, versatile class of materials at elevated temperatures is important in controlling the operation of polymer photovoltaics and has implications in the fundamental factors affecting emission color in PPV based materials.