Photoluminescence of geminate and non-geminate pairs in amorphous semiconductors

Rates of radiative recombination of geminate and non-geminate pairs and the corresponding lifetimes are calculated at thermal equilibrium. It is shown that two kinds of geminate recombinations occur in amorphous semiconductors: (I) through the recombination of the usual geminate pairs (non-excitonic) and (II) through the recombination of those excitons that have relaxed to the tail states. The latter geminate pairs can exist in singlet and triplet spin states, only singlet is considered here, whereas former ones do not have spin dependence. Examples of recent observations and their comparison with the theoretical results are presented.