Abstract: Low-dimensional semiconductors from 0D (quantum dots) to 1D (carbon nanotubes) and 2D (organic molecular assemblies, hybrid perovskites, transition metal dichalcogenides) are gaining immense attention in light-harvesting and light display technologies for their unique optical and electrical properties. Confining light and taming their propagation in these semiconductors will leverage their application in quantum information transfer. Naturally occurring energy transfer in the photosynthesis process forms the foremost transport process of electron-hole bound pairs called excitons. 2D organic molecular assemblies called J-aggregates form an ideal model system to mimic this process. J-aggregates possess a strong extinction coefficient yet suffer from low photoluminescence quantum yield due to non-radiative decay channels.
In this talk, I will present strategies to enhance their emission rate for coherent energy transfer. Using ultrafast spectroscopy studies, a new non-radiative loss called charge-exciton quenching mechanism dictating the emission rate is correlated to the aggregate morphology. Circumventing the non-radiative loss has led to a room-temperature energy transport efficiency of ~60%. Further, tuning the optical absorption of the semiconductors can modify their emission state. Strong light-matter coupling from the semiconductors placed in an external cavity forms exciton-polariton, which are half-light and half-matter states. However, these external cavities limit direct electrode access for external stimuli. 2D perovskites exfoliated on the gold substrate lead to forming exciton-polariton with extraordinary Rabi splitting (~500 meV).
The emergence of exciton-polariton and emission from reflectance and photoluminescence spectroscopy will be presented. Further, exciton-polariton dynamics from ultrafast spectroscopy exhibit Boser action for room-temperature polariton emission in open cavities. Finally, emerging nanophotonic techniques that unravel novel optical phenomena in strained 2D materials will be presented.