Collective behavior of semiconductor nanoparticles for use in solar energy harvesting

We explore different geometries and different composition of semiconductor nanoparticles for the use in solar energy harvesting. Using spectroscopic and photovoltaic measurements, we find that near infrared emitting lead sulfite (PbS) quantum dots (QDs) provide a large increase in performance but suffer from rapid photo-oxidation that results in a decrease in the quantum yield. To address this issue we investigate how the inter- QD interactions affect the degradation of emission properties in QD ensembles. We find that the presence of inter-QD energy transfer (ET) likely contributes to the fast decay in emission intensity that was observed experimentally. Our results indicate that in order to enhance stability of any QD based device it would require a carefully selected ensemble that either minimizes the amount of ET, or has a controlled amount with minimal number of smaller QD