In this work the optical properties of the poly (3,4-ethylenedioxythiophene):poly (styrene sulfonate) (PEDOT: PSS) on glass substrate as interlayer and the effect of temperaturevariation on the optical stability was investigated. Measurement of the transmittance, absorption, extinction coefficient, reflectance, and band gap energy are used to study the influence of annealing on the optical properties of PEDOT: PSS thin film. The thin film had 70% transmittance at 550 nm.It is deduced that as the annealing temperature increases there is increase in absorption of photon energy. It also shows that transmission increases as the wavelength increases and decreases with increases in annealing temperature. As the annealing temperature increases the absorption increases and as the wavelength increases the absorption decreases.Observation shows that band gap energy reduces slightly as annealing temperature is increased from 80oC to 240oC. The band gap energy was approximately 3.7eV.
