In the latter case, their optical recombination can be used to make indirect bandgap materials optically active, as in nitrogen-doped gallium-arsenide-phosphide LEDs.
In organic materials, they are of the Frenkel type, whereas the Wannier-Mott type dominates in semiconductors. While accounting for the effective mass and the host matrix polarizability, the Bohr model can often be used to calculate their energy. In the low-density approximation, they are bosonic, and when strongly interacting with light, their namesake polaritons can show Bose-Einstein condensation through the coherence properties of the emitted light. Although chargeless, they can be bound by quantum wells and dots, interface fluctuations or host matrix impurities. In the latter case, their optical recombination can be used to make indirect bandgap materials optically active, as in nitrogen-doped gallium-arsenide-phosphide LEDs. FTP, what are these composite quasiparticles, consisting of a loosely bound electron and hole?
In organic materials, they are of the Frenkel type, whereas the Wannier-Mott type dominates in semiconductors.
excitons