Non-destructive probing of the anisotropy of field-effect mobility in the rubrene single crystal

Organic single crystals are valuable tools for the exploration of charge transport in organic materials. Here, we report two new methods for the non-destructive probing of anisotropic transport in molecular crystals, demonstrating an angular dependence of the field-effect mobility in the ab-plane of the rubrene single crystal. Clear minima and maxima are observed, corresponding to the a and b principle axes of the crystal, as determined by X-ray diffraction and visual inspection. While this phenomenon has been previously reported, the method presented here offers an angular resolution previously undemonstrated, with methods that eliminate the need to move the fragile crystal. The coincidence of this phenomenon between top- and bottom-contact geometries offers strong support for the performance correlation of mobility with specific molecular orientation, and an improved data set for comparison with transport theory.