What is the exciton Bohr radius? I understand that the exciton is the paired distance of an electron and hole. How does the Bohr radius play a role in this?
The Bohr radius is the radius you get for a free exciton just by considering kinetic energy and the Coulomb interaction. Of course you can reduce the distance between electron and holes by means of confinement as it is done in quantum dots. This results in enhanced Coulomb interaction and discrete energy states as there is no center-of-mass motion.