Project title: The behaviour of charged species in hybrid organic–inorganic perovskite photovoltaics

Supervisors: Prof. Nicholas Harrison (Chemistry), Dr. Piers Barnes (Physics) and Prof. Joost VandeVondele (Nanoscale Simulations, ETH Zürich)

Project description:

Hybrid organic-inorganic perovskites have been known for over a century but only in the past few years have they been studied for potential use as photovoltaic absorbers. The rise in efficiencies of hybrid perovskite based devices has been meteoric, moving from around 3% in 2009 to efficiencies reported at 17 % in 2014 [1],[2]. These high efficiencies and the fact that the hybrid perovskite components can be fabricated using cheap solution based method has generated a huge wave of scientific interest in these materials.

Despite such advances in device efficiency the physics of why hybrid perovskites work so well as photovoltaic absorbers is still poorly understood. In this PhD project, we hope to elucidate some of the physical mechanisms at play in these materials in the hope of optimising current devices or for proposing new materials with similar properties.

Current research has focussed mainly on the hybrid perovskite ‘Methyl-Ammonium Lead Tri-Iodide’ (MAPI), which consists of a lattice of interconnected lead iodide octahedra with an organic methyl-ammonium cation located in the centre of the inorganic ‘cage’ formed by four of these octahedra.

The main aim of this project is to investigate the interaction between the organic cation, the inorganic lattice and the general crystal structure in an attempt to relate these to experimentally observed device behaviour. This will require using techniques spanning a wide range of length and time scales, from Density Functional Theory (DFT) to study the electronic structure through to Molecular Dynamics and Monte Carlo based calculations to investigate dynamical and charge transport phenomena at the level of large crystal fragments or even entire devices.

[1] “Perovskite Fever”, Editorial, Nature Materials 13, 837 (2014).
[2] “The emergence of perovskite solar cells”, M.A.Green, A.Ho-Baillie and H.J.Snaith., Nature Photonics 8, 506-514 (2014).