A series of new organic semiconductors for organic thin‐film transistors (OTFTs) using dithieno3,2‐b:2′,3′‐dthiophene as the core are synthesized. Their electronic and optical properties are investigated using scanning electron microscopy (SEM), X‐ray diffraction (XRD), UV‐vis and photoluminescence spectroscopies, thermal gravimetric analysis (TGA), and differential scanning calorimetry (DSC). The compounds exhibit an excellent field‐effect performance with a high mobility of 0.42 cm2 V–1 s–1 and an on/off ratio of 5 × 106. XRD patterns reveal these films, grown by vacuum deposition, to be highly crystalline, and SEM reveals well‐interconnected, microcrystalline domains in these films at room temperature. TGA and DSC demonstrate that the phenyl‐substituted compounds possess excellent thermal stability. Furthermore, weekly shelf‐life tests (under ambient conditions) of the OTFTs based on the phenyl‐substituted compounds show that the mobility for the bis(diphenyl)‐substituted thiophene was almost unchanged for more than two months, indicating a high environmental stability. A series of new organic semiconductors for organic thin‐film transistors using dithieno3,2‐b:2′,3′‐dthiophene as the core are synthesized (see Figure). The compounds exhibit excellent field‐effect performances, with a high mobility of 0.42 cm2 V–1 s–1 and an on/off ratio of 5 × 106. Devices based on phenyl‐substituted compounds (e.g., 2) have excellent thermal stability and high environmental stability.