Hot Charge Carriers in Quantum Dots: Generation, Relaxation, Extraction, and Applications

This article discusses the hot charge carriers in semiconductor quantum dots (QDs): their generation, relaxation, extraction and applications in different technologically relevant areas. It has been reported that the most common ways to generate hot charge carriers are photo-excitation by energy more than the band gap energy. However, recently the other means to generate hot charge carriers such as doping, and semiconductor plasmon interaction have also been evolved and their advantages over the conventional method have been discussed. Relaxation dynamics of hot charge carriers and different processes related to this such as multiple exciton generation, Auger recombination, phonon vibrations and ligand assisted charge carrier relaxation are mentioned. It was shown that the relaxation mechanism of hot charge carriers (both hot electron and hot hole) follow different pathways and either of the mechanism is playing a role depending on the QDs structure and the surrounding conditions. Studies pertaining to interaction of QDs with other semiconductors, metal nanoparticles or with different molecular adsorbates suggest that the hot charge carrier extraction is possible in these heterojunctions with extraction time in sub-ps scale. Application of hot charge carriers in different fields such as photovoltaics, photo-catalysis, infrared detectors, and H-2 detection have been shown and it was observed that the efficiency of the above-mentioned processes is much higher when the hot charge carriers are involved, suggesting their importance in these areas.