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Physics Colloquium: Matt Beard

April 11 | 4:00 pm - 5:00 pm

Title: Controlling charge, spin and light in Lead-Halide Inspired Hybrid Semiconductors

Abstract: In this presentation I will discuss our studies of controlling the charge carrier dynamics, light/matter interactions, and spin populations in metal-halide organic/inorganic hybrid systems. In one effort we are exploring the use of novel organic hybrid systems at and near interfaces to control the carrier dynamics and reduce surface recombination but also to protect grain boundary surfaces from degradation. With respect to controlling spins we have recently studied and developed a novel class of chiral hybrid semiconductors based upon layered metal-halide perovskite 2D Ruddlesden-Popper type structures.  These systems exhibit chiral induced spin selectivity (CISS) whereby only one spin sense can transport across the film and the other spin sense is blocked.  From these systems we can achieve a high degree of spin current polarization (~90%) and spin-injection when used as a contact layer. We have developed novel spin-based LEDs using mixed NCs as the light emitting layer that promotes light emission at a highly spin-polarized interface.  The LED spin-polarization is limited by spin-depolarization within the MHP NCs.  In a separate effort we have explored the use of chiral copper-halide hybrid systems for circular light polarized detection.  Chiral based copper-halide systems combined with highly conductive carbon nanotube networks can be employed to detect circular polarized light with the use of polarizers. Our chiral heterostructure shows high photoresponsivity of 452 A/W, a competitive anisotropy factor of up to 21%, a current response in microamperes, and low working voltage down to 0.01 V.  Finally, we have developed novel photocatalyst based upon the unique properties of metal-halide semiconductor nanocrystals and show that such systems can drive multiple electron reactions.  These results demonstrate that the emergent properties of organic−inorganic hybrid systems offer unique opportunities in controlling light, charge and spin.

Host: Dali Sun

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April 11
4:00 pm - 5:00 pm
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