Events

Harnessing Spin, Delocalisation and Coherence in Molecular Semiconductors

November 4, 2014 at 4:30pm / 6-120

Akshay Rao
Optoelectronics Group, Cavendish Laboratory, University of Cambridge

Abstract:   For more than three decades the electronic properties of molecular semiconductors have been described as ‘limited by disorder’. Thus, attempts to improve their performance have mainly focused on materials properties such as improving crystallinity and charge mobility. But recent results suggest that some of the most interesting and technologically relevant properties of these systems emerge from the interplay of spin, delocalisalised electronic states, coherent charge motion and vibrational coherence. In this talk I will discuss how these ‘disordered’ materials can harness these phenomena to enable 100% efficient photon to electron conversion in photovoltaics [1-3] and 200% efficient conversion of spin-singlet excitons to spin-triplet excitons via singlet excitons fission. I will also discuss all optical methods to couple singlet fission with conventional inorganic semiconductors [4], with an aim of overcoming thermalisation losses in photovoltaics, and the unique spin properties of helical molecular systems.

[1] Science, 335, 6074, 1340-1344, (2012), [2] Nature 500, 435–439 (2013), [3] Science, 343, 6170, 512-516, (2014), [4] Nature Materials, DOI: 10.1038/NMAT4093, (2014)

 Bio:   Akshay Rao is an Advanced Research Fellow and Group Leader at the Cavendish Laboratory, University of Cambridge. His is interested in the electronic and optical properties of molecular semiconductors, quantum dots and novel nanoscale structures. He has worked extensively on organic photovoltaics as well as singlet exciton fission in molecular semiconductors, using ultrafast spectroscopy to elucidate the how charge delocalisation, spin and vibrational coherence underlie the physics of these systems.    Akshay received his undergraduate degree from St Stephen’s College, University of Delhi in 2006 and his MSc from the University of Sheffield in 2007. He received his PhD from the University of Cambridge in 2011, with Prof. Sir Richard Friend. From 2011 to 2014 he held a Junior Research Fellowship. As of October 2014, he is setting up an independent research group at the University of Cambridge.