Organic compounds containing conjugate (i.e., alternate single-double) bonds can have semiconducting properties. The conductivity and mobility of those organic compounds however, are very low compared to inorganic semiconductors. Assuming the molecules of the organic semiconductor are lattices, the same procedure of electroreflectance of inorganic semiconductors can be applied for the organic ones. It should be noted though that there is a certain dualism in semiconductors: intra-molecular conduction (inside a molecule) and inter-molecular conduction (between molecules), which one should take into account doing measurements. Especially for thin films the band gaps of organic semiconductors can be accurately determined using this method.