Nonradiative trapping and localization in intermediate band solar cells

For intermediate band solar cells (IBSC) to achieve high efficiency, the gains in light absorption due to the intermediate band (IB) must exceed the nonradiative losses from mid-gap states. An important proposal holds that in IB´s formed from bulk doping, when the energy states of the IB are delocalized (i.e., metallic), they do not significantly reduce the nonradiative lifetime. We show that this proposal is incorrect because the motion of the crystal lattice will always relocalize IB states. We compare this result to band-to-band nonradiative recombination, which is well known to be slow. For IBSC´s to realize their potential, research must move away from delocalizing IB states.