A new class of flexible X-ray sensor in which there is a vertical structure with the active layer of minor 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS-pentacene) blending into styrene-ethylene-butadiene-styrene (SEBS) has been developed. The minor TIPS-pentacene to enhance the sensitivity of 1137.2 μCGyair−1 cm−2 and low detection limit of 47.91 nGyair s−1 because of the higher attenuation coefficient and photocurrent gain effect in the hybrid active layer. The stability and flexibility of this organic detector are attributed to the plasticity of SEBS and encapsulation of TIPS-pentacene. This work highlights the potential exploitation of high-performance future innovative flexible and highly sensitive direct X-ray detectors.