Polyaniline (PANI)/pentaerythritol triacrylate (PETA) as gate/gate insulator is introduced to improve the device performance for all-solution-processed organic thin film transistors (TFTs). Direct comparison of the TIPS-pentacene crystal growth patterns on PANI/PETA and on Si/SiO₂ as gate/gate insulators is investigated for the origin of different device performances.