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Simulations of charge transport in organic polymer semiconductors

Department of Physics

About the Project

The University of Bath is inviting applications for the following PhD project supervised by Prof Alison Walker in the Department of Physics.

Semiconducting conjugated polymers are solution-processable and form the basis of flexible electronics. Examples are organic solar cells, light emitting diodes, field effect transistors with many applications in renewable energy, displays and sensors. Organic devices are being developed that manage the interface between electronic devices and cells, tissues and organs. They are also used for charge transport layers in perovskite solar cells, a technology that has attracted much recent interest due to their high efficiencies.

Modelling charge transport in conjugated polymers is important in understanding device performance as it is needed to predict charge mobilities and charge separation processes. The objective of this studentship is to simulate charge transport through conjugated polymer films, both pristine and with chemical and/or conformational defects Polymer film packing arrangements, morphologies, allowing for side chains, will be predicted with the popular LAMMPS code and the SAMSEN code developed by Walker [1]. SAMSEN can simulate film widths of tens of nanometers, typical of those used in devices, on a desk top computer. Charge trajectories will be simulated on these morphologies using the kinetic Monte Carlo, KMC, technique pioneered by Walker [2]. Here we will assume fast intra-chain motion and hopping between chains when in close contact [3]. We will explore temperature variation of the very fast intra-chain charge mobilities which is hard to capture directly from experimental data. Also, we will compare film mobility predictions with measurements of mobility at short times and of charge extraction made by experimental groups, for example at Imperial College. This work ties in with EU and UK projects on modelling organic devices and solar cells which Walker coordinates or in which she is a partner, namely the Centre for Doctoral Training in New and Sustainable Photovoltaics, CDT-PV, EXTMOS, EXTended Model of Organic Semiconductors, the Training Network MAESTRO, MAking pErovskiteS TRuly exploitable and EoCoE, Energy oriented Centre of Excellence in computing applications. These links provide many expert collaborators from academic and industrial groups with a considerable stake in multiscale modelling of polymer devices.

In year 1, the student will focus on polymer film morphologies for different side chain lengths. Year 2 will look at charge transport using KMC and compare charge mobilities for these films at varying applied bias and temperature with experiment. Year 3 will focus on the effects of defects and look at device performance. The final 6 months will focus on writing up the PhD thesis and any remaining publications.

The student will gain highly marketable transferable skills in coding with e.g. Python, using electronic structure packages, data analysis and working across disciplines. He/she will have access to the Bath HPC cluster and 8 servers dedicated to Walker’s group. They will benefit from soft skills postgraduate training offered by the University. He/she will take part in conferences and summer schools in organic optoelectronics and give seminars at University theory/condensed matter and perovskite groups. Outreach activities and contributions to social media, such as Institute of Physics public engagement opportunities, the Pint of Science, and blogs on the CDT-PV website will provide presentation skills and visibility to this project.

Further information about Walker’s research can be found on

Candidate requirements:

Applicants should hold, or expect to receive, a First Class or good Upper Second Class Honours degree (or equivalent) in any of physics, chemistry, mathematics or natural sciences and have a strong interest in coding.

Enquiries and applications:

Informal enquiries are welcomed and should be directed to Prof Alison Walker, .

Formal applications should be made via the University of Bath’s online application form for a PhD in Physics:

More information about applying for a PhD at Bath may be found here:

Funding Notes

We welcome all-year-round applications from self-funded candidates and candidates who can source their own funding.


[1] A R Smith, I R Thompson, A B Walker J. Chem. Phys 150, 164115 (2019)
[2] P K Watkins, A B Walker, G L B Verschoor Nano letters 5 1814 (2005)
[3] L Berencei et al J. Chem. Phys. 151, 064120 (2019)

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