Two-dimensional (2D) semiconductor nanomaterials have recently gathered significant attention due to their remarkable optical and electrical properties. Quantum confinement as resultant of reduced dimensions results in exciting optoelectronic phenomenon, which have never been reported before. This makes them promising candidates for future optoelectronics and photonics device applications. After the discovery of graphene, similar other inorganic 2D materials such as transition metal dichalcogenides (TMDCs) have been extensively researched. This thesis primarily focusses on a new class of organic 2D materials grown through low-temperature vapor deposition process. Simultaneously, it also explores the fundamental exciton dynamics in 2D organic defect-free nanomaterials. We observed an exciting phenomenon of superradiance experimentally from organic 2D materials which has several potential applications in nano lasers and exciton-polariton devices such as Bose-Einstein condensates at room temperature. The thesis also focusses on exploring the dynamics and spatial transport mechanism of excitons in inorganic TMDC materials using near-field and time-resolved PL imaging. In the thesis, we have demonstrated an external engineering control for the exciton transport in monolayer TMDCs using back gate voltage.

The thesis further explores the dimensionality engineering of excitons in to a 2D, 1D and quasi-0D space to enhance their properties for suitable optoelectronic device applications. We have further demonstrated a 1D organic nanowire with exciting optical properties that can be used for organic display screens and lasers. The exciton dynamics have been studied and reported at various temperatures to understand the nature of excitons as the dimensionality changes from 2D to 1D. In organic materials such as phosphorene, I have demonstrated an experimental approach to generate a 2D-1D-0D hybrid system of excitons. The properties demonstrated have tremendous applications in future optoelectronic devices.

Finally, the thesis demonstrates a first of its kind 2D organic-inorganic hybrid semiconductor heterojunction, which has high efficiency for light to electricity conversion ration and vice-versa. The organic and inorganic part are both atomically thin and that resulted in exciting optical properties that have been demonstrated through various experimental results.

In sum, this thesis is focussed on exploring the fundamental excitonic dynamics and properties in novel 2D organic and inorganic atomically thin semiconductor materials for their applications in next generation miniaturized optoelectronic, electronic and photonics devices.

This seminar is the final Ph.D. seminar for Research School of Engineering Doctoral Student, Ankur Sharma.