AbstractAmong various photoresponsive materials, organic materials have gained interest due to their low cost, large‐scale yields, and compatibility with flexible substrates. However, their low photoresponsivity compared to inorganic counterparts has been consistently pointed out as a limitation. To address this issue, a highly photoresponsive PM6:Y6/IGZO hybrid phototransistor is presented with a broad spectral range of 450–950 nm. The photoresponse of the device is enhanced by controlling the PM6:Y6 blending ratio, active layer thickness, and solvent additive treatment. The PM6:Y6 blending ratio and thickness are optimized to promote charge separation and efficient charge transport, leading to a significant increase in photoresponsivity. Moreover, solvent additives are employed to improve the crystallinity of the PM6:Y6 film, which further enhanced the charge transport. As a result, the PM6:Y6/IGZO hybrid phototransistor exhibited exceptional performance, with an ultrahigh photoresponsivity of 2.2 × 10⁸ A W⁻¹ and specific detectivity of 9.8 × 10¹⁶ Jones under 750 nm light with an intensity of only 1.03 nW cm⁻². These results highlight the potential of organic materials in developing high‐performance phototransistors.