Organic phototransistors capable of absorbing in the visible light spectrum without color filters are the best alternatives to conventional inorganic phototransistors. In this study, the effect of illumination on the electrical characteristics of a solution-processed poly(3-hexylthiophene): 6,13-bis(triisopropylsilylethynyl) pentacene-blend thin-film transistor (TFT) was investigated. The wavelengths of the irradiated light were determined from the absorbance spectrum of the blended film and changes in the transistor's electrical characteristics were explained in relation to the electrical and light absorption properties of each component material. The photosensitivity and absorbing properties of the blended TFT were enhanced at 515 and 450 nm and exhibited positively shifted threshold voltages under incident light. The results indicated that the photo-generated exci-ton pair characteristics matched the absorbance properties of the blended material and that the absorption and photocurrent characteristics of the respective components could be combined. This process for the heterogeneous blending of organic semiconductors has the potential to improve phototransistor performance and contribute to the development of broadband absorbing phototransistors.