A series of functionalized pentacene derivatives based on symmetric and asymmetric substitutions of the terminal rings are synthesized (see figure). Field-effect mobilities as high as =0.23 cm(2) V-1 s(-1) are obtained with 2,3-dibrompentacene. These devices show improved stability compared to pentacene and exhibit no significant decrease in mobility or on/off ratio when stored in air, with and without light exposure, even after three months.