Quantum dot and quantum well solar energy converters

We review designs of a solar cell constructed from pn junctions, quantum dots and quantum wells. In the first instance we show that quantum wells of varying size embedded in the depletion region yields spatial variation of the energy gap that can be controlled. An advantage of the proposed structure is efficient utilization of the broad solar spectrum, lessening of lattice matching problems and generation of electron-hole pairs in narrow depletion regions which yields fast spatial separation of charges and, thus, reduces recombination losses. In another model we show how quantum coherence can be used, in principle, to eliminate radiative recombination and increase photocell power.