Intermediate band photovoltaics hold the promise of being highly efficient
and cost effective photovoltaic cells. Intermediate states in the band gap,
however, are known to facilitate nonradiative recombination. Much effort has
been dedicated to producing metallic intermediate bands in hopes of producing
lifetime recovery -- an increase in carrier lifetime as doping levels increase.
We show that lifetime recovery induced by the insulator-to-metal transition
will not occur, because the metallic extended states will be localised by
phonons during the recombination process. Only trivial forms of lifetime
recovery, e.g., from an overall shift in intermediate levels, are possible.
Future work in intermediate band photovoltaics must focus on optimizing subgap
optical absorption and minimizing recombination, but not via lifetime recovery.Comment: 8 page
