Furthermore, this change in permittivity due to illumination caused an impedance mismatch, leading to in-creased insertion/return loss and return loss across the CPW. To further understand the observed increase in insertion loss due to the increase in conductivity under illumination, we conducted COMSOL simulations and results in presented in Figure ). The simulations revealed that the higher conductivity of the PM6:Y7 blend resulted in higher conduction losses along the transmission lines and within the dielectric material itself. These losses were particularly prominent at higher frequencies, where the skin effect became more pronounced, causing the electric current to concentrate near the surface of the conductors 37 . Consequently, this concentration of current along with the space charge buildup near the metal/blend interface (leakage current) exacerbates the losses associated with the higher conductivity of the illuminated PM6:Y7 blend, resulting in elevated insertion/return loss across the CPW. This observation is crucial as it underscores a potential limitation in the usage of the PM6:Y7 blend in environments with variable lighting, particularly in applications requiring precise impedance matching and phase control.