The Role of Polymorphism in Modulating Charge Transport Properties of Perylene-DTTCNQ Cocrystals

Abstract

The charge transfer properties of organic molecular semiconductors are closely related to the accumulation of molecular crystals. Based on quantum nuclear tunneling model, the effect of polymorphs on the charge transport properties of binary charge-transfer complexes composed of perylene and 4,8-bis(dicyandiylidene)-4,8- dihydrobenzo[1,2-b:4,5-b']-dithiophene (DTTCNQ). Analysis of the reorganization energy of molecular crystals using the four-point (4P) method. Perylene was analyzed using the normal mode (NM) method, and the middle frequency around 1500 cm-1 made the largest contribution to the reorganization energy, followed by the low frequency in the neighborhood of 500 cm-1. In the α-phase crystal, the maximum anisotropic mobility of the hole and electron are in the xy and xz directions, respectively, and those in the β-phase crystal are in the xy and yz directions, and anisotropic mobility are closely related to the transfer integrals. The α-phase crystal is more stable than the β-phase as a ambipolar material. The polymorphism of perylene-DTTCNQ crystals gives rise to different molecular stacking in the α- and β-phases, resulting in a large difference in the charge transport properties of the α- and β-phases.