Salzberg Chemistry Seminar guest speaker Dr. Vladimir Mitin
Mon, Apr 28
12:00 PM — 1:00 PM
Marshak Hall160 Convent Ave
Marshak Hall, MR-1027
Nanomaterials with charged quantum dots for solar energy conversion & advanced sensing applications"Nanomaterials with charged quantum dots for solar energy conversion and advanced sensing applications" guest speaker Dr. Vladimir Mitin, University at Buffalo, The State University of New York, Buffalo.
SEMINAR ABSTRACT: The presentation focuses on design, fabrication, and characterization of novel quantum dot (QD) structures with potential profile engineering and manageable kinetics of photoelectrons. Our approach is based on engineering of photoelectron capture processes using various configurations of manageable potential barriers around separated QDs and collective barriers around QD clusters. Potential barriers around QDs are always created, when electrons from dopants outside QDs fill the dots. To effectively control photoelectron capture processes, the barrier height should be of the order of the thermal energy of electrons. Such barriers can be created by Quantum dots with Build In Charge (Q-BIC) that is controlled by the type and by the level of doping. By combining Q-BIC with various positions of dopants it is possible to create unique distribution of potential barriers, which forces photoelectrons to move in designated direction without capturing into the QDs. Besides manageable photoelectron lifetime, the novel structures provide also stronger coupling to radiation, high scalability, low generation-recombination noise in sensing applications and effective harvesting of infrared energy in Q-BIC solar cells. It was experimentally demonstrated that responsivity of QD infrared photodetectors at nitrogen temperatures can be increased by more than 30 times using Q-BIC structures. Experimentally demonstrated increase of the short circuit current due to additional absorption in QDs is at least 9 mA/cm2 that lead to a substantial increase in the efficiency of solar cells with InAs Q-BIC in GaAs (the highest short circuit current in GaAs solar cells is about 29 mA/cm2, so GaAs with Q-BIC solar cells should give at least 37 mA/cm2 current).
The major part of the talk is based on the works made in collaboration with K. Sablon, A. Sergeev, G. Strasser, J. W. Little, K. Reinhardt, S. Oktyabrski, and N. Vagidov.