crystals!

Lately there has been some talk about the importance of crystallography on Whistling in the Wind and Chemical Musings. While some interesting points about modeling in general and drug design in particular come up, some of us who are less interested in pharma-chem are still in need of crystallographic data.
Semiconductors, the molecular love-children of people who design materials for use in devices such as transistors (and solar cells and OLEDs and others), have electronic properties that are closely related to their crystal structures.[1] Charge carrier mobility in crystals of organic semiconductors depends on the crystallographic axis along which the mobility is measured. In other words, if you're trying to build a single-crystal transistor, you had better have a crystal structure so you can tell how to orient the thing for highest mobility. More importantly, the band structure of a semiconductor depends on its crystal structure. (Although I would really like to go into more detail here, k-space really hurts my head.) I will probably elaborate on this topic after a semester's worth of crystallography. Until then, ask your local crystallographer or solid-state physicist, or consult the Britney Spears guide to Semiconductor Physics.

Have a picture. Here's the band structure of silicon carbide (not organic, but good enough as an example of sorts.)

Taken from here

[1] Polymers are an exception of sorts, since they are too weird to have regular crystal structures...