We have created some new projects that are a combination of chemical and physical research. The work still has a firm foundation in nanophotonics, but is focussed more on the development of new optical materials. We have established strong links with other research groups whose interests range from synthesis chemistry through to device and theoretical physics. Our long term objective is a molecular structure-property relationship that will provide the rules for conceiving new optical materials on a molecular level. Our current research programmes fall in to four categories:
Structure-property relations in organic crystals
One of the most exciting prospects of using molecular materials for optical applications is the opportunity to exploit the established procedures of chemical synthesis to modify and optimise the molecular structure to suit specific objectives. This requires the understanding of the relationship between the property of the material and the structure of the molecule from which it is prepared. We use photoluminescence spectroscopy to analyse new compounds that exhibit novel photophysical properties.
We have developed a wealth of experience in the characterisation of such materials using continuous and time-resolved confocal fluorescence microscopy. We are especially interested in the optical, electronic and morphological properties of molecular nanowires.
Lasing from organic nanocrystal
Organic semiconductor materials synthesised as nanocrystals exhibit photophysical properties that differ markedly from both bulk materials and molecules and offer the opportunity to investigate excited state species confined in a single nanocrystal.
We have developed a range of new expertise including the growth of organic semiconductor materials that have strong potential for new types of lasers known as exciton-polariton systems. Our goal is to develop organic materials and devices with quantum properties leading to new or enhanced functionality, such as low-threshold organic laser.
Vertical Single-Crystalline Organic Nanowires
Direct epitaxial growth of organic semiconductor nanowires on lattice-matched substrates has provided an important way to fabricate light sources for various applications including lighting, displays and optical communications. We developed a facile solution-based strategy for the growth of vertical organic semiconductor nanowires. Micro-photoluminescence (μ-PL) experiments were carried out by exciting the nanowires with a laser and collecting via a confocal microscope setup enabling micrometer-range spatial resolution. The well-defined spectrum from a single nanowire demonstrates high quality of such optical cavity, without any apparent contamination due to the growth process. The mode spacing depended on the crystal lengths, indicating that the nanowires can confine photons between two opposite facets, establishing Fabry-Pérot modes. This strategy may ultimately form the basis of future monolithic light sources needed to bridge the existing gap between organic-based photonic and electronic circuits.
Organic-Inorganic Lead Halide Perovskites: from Bulk to Nano
Perovskite materials are arising as a new generation of solution processable organic-inorganic hybrid photonic materials. Our research on perovskite photonics involves in:
- Materials synthesis for the lasing applications.
- Understanding the fundamental material and devices physics to explore the highest quantum efficiency;
The work forms the part of key collaborations with both industry and academe.