Apart from the development of new dielectric and semiconductor materials, the semiconductor–dielectric interface study is also very important for the optimum performance of organic thin film transistors (OTFTs). Herein, we have reported the detailed synthesis of a whole new family of dielectric materials which are 1,3,5,7-tetrabromoadamantane; 1,3,5,7-tetrachloroadamanatane; 1,3,5,7-tetraiodoadamantane and 1,3,5,7-tetrauraciladamantane (AdUr₄). The unique ability of these molecules to undergo supramolecular thin film formation at low temperature, was analysed for their potential use as an insulator in organic electronic devices. Owing to the good leakage current density property shown by AdUr₄ dielectric material it was further employed as a gate dielectric in regioregular poly(3-hexylthiophene), (P3HT) based OTFT. This OTFT device which was fabricated on a flexible PI plastic substrate has shown a good on/off current ratio (e.g., 2.18 × 10⁴) and high mobility (e.g., 0.15 cm² V⁻¹ s⁻¹). The semiconductor–dielectric interface study, has revealed that the AdUr₄ gate dielectric layer has guided the P3HT molecular chain domains to undergo edge-on orientation, which is the charge transport direction in OTFTs. In this process, the grazing incidence X-ray diffraction (GI-XRD) analysis and AFM study was also employed.