Small molecule semiconductors; experiment and theory

(supervisor: Chris Finlayson)

Nature of project: experimental, theory

Available to full-time physicists only.

Project description and methodology

Semiconducting small molecules represent a technologically important class of organic materials.[1] The electronic structure of pi-orbitals in such polymers enables them to absorb light and to generate free charge-carriers, as is seen to occur in solar cells and in natural processes such as photosynthesis. The use of organic semiconductors in electronics and in photovoltaic/solar cells, as a low-cost alternative to silicon based materials, is currently an area of intense scientific research and environmental interest.

In this project, students will study the optical properties of particular classes of molecules, known as perylenes/phthalocyanines,[2] as supplied by collaborators from the University of Nijmegen.[3] This will involve experimental measurement of (e.g.) absorption, photoluminescence, and quantum-yield in various solvent media. Using the Gaussian quantum-chemistry software[4] recently acquired by the department, students will also be simulating the electronic structures of these molecules, in order to better understand the observed characteristics.

A successful project will develop beyond the above in one/some of the following directions:
A deeper understanding of the underlying photophysics, and its correlation to quantum-chemical models will involve some theory well beyond the standard UG syllabus, and will provide a challenge to more capable/enthusiastic students.

When considering where to take your project, please bear in mind the time available. It is preferable to do fewer things well than to try many and not get conclusive results on any of them. However, sometimes it is useful to have a couple of strands of investigation in parallel to work on in case delays occur.

Additional scope or challenge if taken as a Year-4 project: In Y4, the development of suitable solvation models would be an example of the additional scope possible.

Initial literature for students:

  1. A. Moliton, Polymer International, vol.53, p1397–1412 (2004)
  2. S. Albert-Seifried, Chem. Eur. J., vol.16, p10021-10029 (2010)
  3. Chen Li, Adv. Mater. vol 24, p613 (2012)
  4. http://www.gaussian.com/g_prod/g09.htm

Novelty, degree of difficulty and amount of assistance required

Students will need to be trained on a number of pieces of lab equipment and to observe basic chemical safety protocols. Appropriate assistance and training will be given.

The basic aims of the project as set out make it suitable for Y3 students, but with the scope for it to be a challenging Y4 project also. A basic knowledge of chemistry would also be advantageous for this project.

Project milestones and deliverables (including timescale)

milestoneto be completed by
Lab training / software familiarisationChristmas
Data collectionend of February
Running of simulations mid-March
Collation and analysisEaster

Students taking this project will have to submit a full risk assessment form