Background: Molecule chain orientations of conjugated polymer have dramatic influence on corresponding device performance

which can be controlled by the methods such as varying the solvents with different boiling point. Purpose: We attempted to study the influence of solution concentration on orientation and related carrier mobility of P3HT thin film. Methods: The P3HT thin films were made by spin-coating from chloroform solution of different concentration and characterized using UV-Vis absorption spectra

grazing incidence X-ray diffraction. The organic thin film transistors were also fabricated to characterize the corresponding mobility. Results: The absorption peaks of the thin film prepared with low concentration solution red-shifted compared with that of high concentration. In out-of-plane GIXRD the relative intensity of(100) peak increased with decreasing concentration while the(010) peak moved in reverse.(100) diffraction dot in 2D GIXRD of thin film prepared with high concentration solution was mainly in out-of-plane direction while that with low concentration solution was mainly in in-plane direction. Conclusion: Based on the above results

the orientation changes from face-on orientation to edge-on orientation as the solution concentration decreases

which achieves the same effect with that of high boiling point solvents and enhances the mobility. It is possibly due to that low concentration solution needs more time to evaporate.