Solar cell with an intermediate band of finite width

This article considers idealized solar cells whose absorbers are intermediate band (IB) media with finite bandwidths that permit both interband and intraband photoinduced electronic transitions at states within the IB. To comprehend the effect of the IB width, three classes of IB absorbers are constructed where each class is distinguished from the others by its spectral selectivity. It is shown that (i) the maximum-power efficiency tends gradually toward zero with increasing bandwidth when photoinduced interband transitions and intraband transitions are equally likely; (ii) with respect to the former, a relative efficiency enhancement may occur when photoinduced intraband transitions dominate interband transitions; and (iii) although thermodynamically consistent, efficiencies may be physically inconsistent without including photoinduced intraband transitions. Resulting from the solar surface temperature of 6000 K, the authors conclude that the largest efficiencies result when the IB width is roughly equal to or less than 800 meV.