Formation, growth, and electronic properties of microcrystalline organic semiconductors

Even though record organic semiconductor mobilities are reported for organic semiconductor single crystals, making thin film crystals remains difficult. We will show our efforts to understand crystal formation, epitaxy, and transport. In particular, we will discuss our efforts to realize pinhole free films of numerous organic semiconductors with 100s microns scale grains, and how the materials able to undergo a transition from amorphous to crystalline correlate well with thermal properties. Homoepitaxial studies uncover evidence of point and line defect formation in these films, indicating that homoepitaxy is not always strain-free. Transistors made out of large-grained films of rubrene display charge carrier mobility of up to 3.5 cm2 V–1 s–1, very close to single crystal values, highlighting their potential for practical application. Finally, we will show efforts in achieving heteroepitaxial growth of a different molecular material on top of a crystalline organic template.