Orateur
Christophe Delerue
(IEMN, Université de Lille)
Description
Carrier-multiplication (CM) is a process in which more than one electron-hole pair is created as the result of the absorption of a single photon. CM in semiconductor quantum dots (QDs) has recently received considerable attention both experimentally and theoretically. But the results are subjects of important controversies and therefore it is still not clear whether CM in QDs has the potential to improve the performance of solar cells. The main origin of CM is the relaxation of photo-excited carriers by impact ionization which, above a certain energy threshold, becomes more efficient than the intraband relaxation by emission of phonons.
In this presentation, we review recent theoretical works on the physics of CM in QDs. Critical assessment of these works will be done. We present calculations of impact ionization rates, carrier-multiplication yields and solar-power conversion efficiencies in solar cells based on quantum dots (QDs) of α-Sn and HgTe. Using these results and previous ones on PbSe and PbS QDs, we discuss a strategy to select QDs with the highest carrier-multiplication rate for more efficient solar cells. We show that the improvement of the maximum solar-power conversion efficiency remains a challenging task.
