Vapor-to-glass preparation of biaxially aligned glassy liquid crystal

Physical vapor deposition (PVD) provides a unique tool for the additive manufacture of organic light-emitting diode (OLED) displays, where high surface molecular mobility and surface equilibration provide excellent control of molecular order. While existing work has demonstrated that out-of-plane uniaxial symmetry can be prepared by PVD below T_g, here in this work we introduce the additional dimension of in-plane alignment by combining conventional substrate alignment into PVD. With the collective effect of substrate templating and surface equilibration mechanism, biaxial bulk alignment is achieved up to 50 K below T_g with single-component disk-like (phenanthroperylene ester) and rod-like (itraconazole) mesogens. The structural anisotropy is characterized by GIWAXS and the optical anisotropy is measured with polarized optical microscopy, where 70% degree of polarization can be obtained in the 250 nm PVD film. Practically, this presented preparation of biaxially aligned mesogens points out the possibility to add an ordered and highly customizable individual layer into a device directly from vapor at low processing temperature without risking destroying the structure in the underlying layers, which may lead to the development for next-generation organic electronic devices.