Research Themes

Our research is focused on the spectroscopy of molecular materials to explore fundamental scientific issues related to using the functional molecules for electronic applications.  Our work lies at the interface of physics, materials, and physical chemistry. Research in molecular electronics has a very broad scope with many promising applications, including: solar cells, displays, transistors, biosensors and photonic device applications. Despite the diversity of uses, all these applications are based on thin films of functional materials such as organic semiconductors and organic/inorganic hybrid materials.   In each case their performance is critically dependent upon the structural and optoelectronic properties of molecules, the precise arrangement, packing and interactions between the molecules. Our principal research focuses on this fundamental issue, seeking to develop a systematic, microscopic understanding of the relationship between nanostructures and optoelectronic properties of molecular semiconductors and to correlate it with the device functionality and performance.

 Twist and Degrade—Impact of Molecular Structure on the Photostability of Nonfullerene Acceptors and Their Photovoltaic BlendsIn this regard, our team has been developing advanced optical and structural probes for molecular semiconductors. For example, we have developed and established Raman spectroscopy as an advanced structural nanoprobe for conjugated molecular semiconductors. Utilising selective resonant and polarisation dependent excitations, together with in situ control of temperature, pressure, electrical, and electrochemical potential, we have demonstrated its unique capability to elucidate the properties of molecular semiconductors. These include chemical structure, molecular conformation, order, orientation, fundamental photo- and electro-chemical processes and stability - all of which are critically important to the performance of a wide range of optical and electronic organic semiconductor devices.

Our ambition now is to extend our expertise towards the field of Nanoscale Functional Materials including organic and organic/inorganic, perovskites, bio-nanomaterials for hybrid electronics targeting for photo-electron conversion and bio applications, paralleled with developing novel spectroscopic Nanometrology for these functional materials.

Research Areas

Organic Photovoltaic

One of the most promising research topics in the field of energy materials is the production of solar cells based on Organic Molecules. Organic Photovoltaic (OPV) offers a wide variety of advantages, especially the possibility to create low-cost, light-weight, transparent and flexible devices which can be embedded into everyday objects for clean energy harvesting.

In our research group we study new organic molecules for OPVs, with a special focus on Non-Fullerene Acceptors, to gain nanoscale insight into their photo-conversion mechanisms. In particular, the fact that our devices are based on bulk heterojunction active layers, i.e. an interpenetrating network of different semiconductor molecules, complicates the process of electron-hole separation and extraction at the interfaces and makes detailed studies necessary to optimise device architectures and production routes. 

In our laboratories we fabricate solar cells by solution-based processes like spin-coating and characterise them by a variety of techniques. Some of the highlights of our equipment are Kelvin Probe and Ambient Pressure Photoemission Spectroscopy to investigate materials energy levels, Raman Spectroscopy for a thorough analysis of molecular vibrational modes and Atomic Force Microscopy to get surface images with nanometric resolution, as well as standard testing methods like electrical measurements in the Solar Simulator. 

Energy diagrams and Raman
J. Luke et al. Adv. Energy Mater. 2019, 1803755

Since one of the most important requirements to achieve an effective large-scale OPV production is a stable long-term device performance, our research also aims at an in-depth understanding of the degradation processes undergone by the molecules. Methods like temperature-dependent Raman help us to probe the ageing mechanisms in the materials in order to improve their stability under operating conditions.