Bidimensional H-Bond Network Promotes Structural Order and Electron Transport in BPyMPMs Molecular Semiconductor

The presence of a hydrogen bond (H-Bond) network has been proved to impact significantly the efficiency of organic light-emitting diode (OLED) devices by promoting molecular orientation and structural anisotropy in thin films. The design of specific compounds to control H-Bond network formation in an amorphous material, and hence to improve OLED performances, is needed. A successful example is given by the bi-pyridyl-based family n-type of organic semiconductors named BPyMPM. The experimental evidences demonstrate a surprisingly higher electron mobility in thin film composed of 4,6-bis(3,5-di(pyridine-4-yl)phenyl)-2-methylpyrimidine (B4PyMPM (B4)), which is almost two order of magnitude higher than mobility measured for very similar member of the family, 4,6-bis(3,5-di(pyridine-2-yl)phenyl)-2-methylpyrimidine (B2PyMPM (B2)). Herein, a comprehensive computational study is presented, wherein classical and ab initio methods are combined, to investigate the 2D H-Bond network in B4 and B2 thin films. The results indicate that B4 forms a larger number of intermolecular C-H···N H-Bonds that promote a higher orientational and positional order in B4 films, and superior electron transport properties.