Final answer:
In solution-cast polycrystalline organic semiconducting thin films, the focus is on 'Interdomain orientational and structural heterogeneity' as it affects material properties.
Step-by-step explanation:
In the context of solution-cast polycrystalline organic semiconducting thin films, the key focus of discerning variable extents is b) Interdomain orientational and structural heterogeneity. This is because differing orientations and structures between domains in a polycrystalline material can have significant effects on the properties of the material. For example, in the presence of an external field, the domains in a material will tend to align with this field to minimize the energy of the system. However, in polycrystalline materials, there can be variations in how domains align, which is why discerning the extent of interdomain heterogeneity is crucial for understanding and optimizing the performance of these materials. Understanding the degree of orientational and structural heterogeneity among domains can give insights into the electrical and mechanical properties of semiconducting thin films, which are important for applications in flexible electronics and other devices.