Disclosed are a copolymer of a perfluoropolyether derivative and a photosensitive polymer, a composition for forming banks comprising the copolymer, and a method for forming banks using the composition. Also disclosed is an organic thin film transistor including the composition and an electronic device including the organic thin film transistor. The use of the copolymer may enable the formation of banks by a solution coating process. Because an organic thin film transistor including banks formed by the method may be fabricated without any degradation in the characteristics of the organic thin film transistor, improved electronic properties may be exhibited.