Glasses are generally regarded as disordered and the idea of “controlling” molecular packing in glasses is reasonably met with skepticism.  However, as glasses are non-equilibrium materials, a vast array of amorphous structures are possible in principle. Physical vapor deposition (PVD) produces glasses with properties that cannot be achieved by other preparation routes, including high stability and controlled anisotropy. The exotic properties of PVD glasses can be explained by a surface equilibration mechanism: mobility near the free surface allows substantial equilibration during deposition, even well below the conventional Tg. Initial work with organic glasses has now been extended to show aspects of ultrastability in metallic and chalcogenide glasses.

The active layers in commercial OLEDs are PVD glasses of organic semiconductors. Ultrastable glasses of organic semiconductors make longer-lasting OLEDs and in-plane orientation of emitter molecules produces more efficient OLEDs.  Co-deposition of two organic semiconductors often produces a homogeneous ultrastable glass but, in other systems, component separation occurs in the plane of the sample, on a controllable length scale.