Optically-tunable organic semiconductor heterojunction P3HT-PCBM for millimeter-wave applications

The dielectric constant of a photo-sensitive organic semiconductor heterojunction poly(3-hexylthiophene) (P3HT, 95%) and [6,6]-Phenyl C61 butyric acid methyl ester (PCBM, 5%) is estimated using its transmission response using a vector network analyzer driving a quasi-optical (QO) transmissometer. White-light irradiance of 65mW/cm² over an area of 2.27cm² is used to promote the photo-induced dielectric response of the organic polymer blend; so defining the `active´ state. Estimation of the complex permittivity of the polymer-blend is undertaken for both inactive (dark-state), and active state conditions to observe its tunable dielectric range over the WR-3 waveguide band (220-325 GHz).