Lab exchange grant: circularly polarized photoluminescence (CP-PL) imaging

Dr Jessica Wade, Lecturer in Functional Materials at Imperial, was awarded an M4QN laboratory exchange grant so that one of her students, Louis Minion, could to visit the lab of Professor Robert Pal, University of Durham.

The purpose of the visit

Louis writes:

“I used this opportunity to visit the laboratory of Professor Robert Pal, at the University of Durham, where I met researchers in the group, discussed experimental methods and techniques, and used their equipment to measure specialized techniques including Circularly Polarized Photoluminescence (CP-PL) spectroscopy and circularly polarized photoluminescence imaging and microscopy. I used the time to measure several samples of a chiral polyfluorene film and discover unusual features in its spectra which offer insights into the structure and electronic properties of this film. This is of great interest to the community because chiral polyfluorenes offer very strong chiroptical properties but the structural origin of this is not fully understood. The instrumentation they had allowed me to measure the CP-PL as a function of excitation wavelength, vital for ruling out one possible mechanism for the unusual spectral features. This technique was not available at Imperial College.

Additionally, my time in Robert Pal’s lab allowed me to discuss the technique of CP-PL with several experts including Professor Pal, increasing my understanding and benefiting my attempts to recreate this method at Imperial College. Their insights were crucial to helping me refine the calibration procedure for experiments carried out at Imperial.”

Benefits to the UK materials and quantum community

“The development of chiral organic materials with strong responses to circularly polarized light (CPL) is of great importance to the UK quantum materials community for a number of reasons. Chiral materials offer the ability to control spin via the CISS effect, circularly polarised light offers key advantages for technologies, and more. Developing materials with strong CPL response requires strong understanding of structure-property relationships as well as robust measurement techniques. Using the visit I was able to measure the CPL response of several key organic thin films, as well as gain experience in the implementation of CP-PL instruments, working towards both above goals.

The Materials for Quantum Network has two overall key aims: the formation of a new interdisciplinary research community, and the identification of new interdisciplinary research topics. This visit allowed me to work towards both aims. By forming new links with the research group at Durham, I made a step towards creating an interdisciplinary community and began to develop an interdisciplinary topic. The researchers I visited worked mainly on using CP-PL to measure inorganic systems, and development of CP-PL related techniques. I visited their lab and used the equipment to examine organic thin films, broadening the horizons of their techniques and beginning an interdisciplinary collaboration.”

Visit outcomes

“The visit identified a key feature in the CP-PL spectrum of a chiral polyfluorene film and confirmed that its measurement was not an artefact (as had been previously suspected). Given the relatively short visit, no new papers or funding applications have been made yet, but the results obtained are of great importance to a publication under preparation.”