Fibers are promising materials being utilized in electronics, principally in the areas of capacitors and sensors. In this study, we examine the effect of pyrolysis temperature on the electrical conductive behavior and photosensitivity of a carbon-based fiber, which was made by electrospinning a polymer solution containing polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), and dimethylformamide (DMF). Converting the polymeric fiber into a carbon fiber was performed through the controlled pyrolysis during which oxidation, stabilization, and carbonization happened. After oxidation at an elevated temperature, the linear polymer fiber was stabilized to have a backbone structure. Then the oxidized fiber was treated in an even higher temperature range to be partially carbonized under the protection of argon gas. We utilized multiple samples of the fibers treated at various pyrolysis temperatures inside a heat furnace and examined the effects of the temperatures on the properties. The partially carbonized fiber is highly active in view of electron generation under photon energy excitation. The unique electrical and photovoltaic property are due to their semiconducting behavior. The morphology of the specimen before and after the pyrolysis was examined using scanning electron microscopy (SEM). The SEM images displayed the shrinkage of the fiber due to the pyrolysis. There are two stages of pyrolysis kinetics. Stage I is related to the oxidation of the PAN polymer. Stage II is associated with the carbonization and the activation energy of carbonization is calculated as 118 kJ/mol.