The study of ambipolar charge carrier transport in organic thin films transistors (OTFTs) is relevant to understand the device physics of light emitting organic transistors. Ambipolar OTFTs require injection of holes (h<sup>+</sup>) and electrons (e<sup>-</sup>), which translates into a good matching between the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels of the organic semiconductor and the work function of the electrodes used for h<sup>+</sup> and e<sup>-</sup> injection. Within this context, we report on two cases of study. The first case concerns a novel class of S-oxide and S,S-dioxide inner-core dithienothiophene oligomers showing tunable electron affinities and structure-property relationships in solution-deposited films<sup>1</sup>. The second case concerns solution-deposited films of a pentacene derivative, 2,3-dicyano-6,13-bis-(triisopropylsilylethynyl)pentacene (2,3-CN2-TIPS-Pn). In these films, a well balanced ambipolar charge transport is observed (the values of the h<sup>+</sup> and e<sup>-</sup> mobility are both about 2⋅10<sup>-3</sup>3 cm<sup>2</sup>/Vs). The positions of the HOMO and LUMO of2,3-CN2-TIPS-Pn with respect to the work function of the Au charge-injecting electrode and the arrangement of the molecules in the film, as deduced by grazing incidence X-ray diffraction analysis, contribute to explain the charge transport properties of 2,3-CN2-TIPS-Pn films<sup>2</sup>. <sup>1</sup>C.Santato*, L.Favaretto, M.Melucci*, A.Zanelli, M.Gazzano, M.Monari, D.Işık, D.Banville, S. Bertolazzi, S.Loranger, F.Cicoira J. Mater. Chem. (2010) 20, 669-676. <sup>2</sup>D. Işık, Y. Shu, G. Tarabella, N. Coppedè, S. Iannotta, F. Cicoira, L. Lutterotti, J. E. Anthony, C. Santato* Ambipolar organic thin film transistors based on a soluble pentacene derivative, accepted for publication in the journal Appl. Phys. Lett.