We are currently working on two EPSRC-funded projects; one on perovskite solar cells (PSC) and the other on dye-sensitized solar cells (DSSC)
Self-assembling Perovskite Solar Cells
I am PI on a £2.5M EPSRC grant (EP/M015254/1) working with Prof Henry Snaith FRS (Physics, Oxford) and Prof Dave Worsley and Dr Trystan Watson (Engineering, Swansea) to study self-assembly approaches towards roll-to-roll (R2R) manufacturing of perovskite solar cells on flexible substrates. In this context, self-assembly can be defined as a process by which perovskite device sub-components adopt a desired device arrangement without external input.
Our group is designing and synthesising device sub-components to enable self-assembly and then to develop in situ metrology (e.g. spectroscopy, visualisation) to monitor the self-assembly and overall manufacturing progress. To date, we have identified limitations of toxic manufacturing solvents1,2and developed solvent-free self-assembly of perovskite onto metal oxide scaffolds leading to the development of inks based on benign solvents3. The resultant perovskite films also exhibit enhanced stability to humidity and air exposure. We are currently extending the self-assembly approach to Pb-free perovskites and to other device sub-components (e.g. substrates, charge carrying layers).
1 A.E. Williams, P.J. Holliman, M.J. Carnie, M.L. Davies, D.A. Worsley, T.M. Watson, J. Mater. Chem. A, 2014, 2, 19338.
2 P.J. Holliman, A. Connell, E.W. Jones, S. Ghosh, L. Furnell, R.J. Hobbs, Materials Research Innovations, 2015, 19, 508-511.
3 E.W. Jones, P.J. Holliman, A. Connell, M.L. Davies, J. Baker, R.J. Hobbs, S. Ghosh, L. Furnell, R. Anthony, C. Pleydell-Pearce, Chem. Commun., 2016, 52, 4301-4304.
Self-assembling Dye-sensitized Solar Cells (DSSC)
The major challenges for scaling DSSC technology for wider product use are improving device efficiency, manufacturing and lifetime. Improving efficiency requires dyes which extend spectral response to λ > 650nm to increase light harvesting. To achieve this, we have pioneered rapid co-sensitization of multiple dyes1-3. This approach is preferable to using panchromatic dyes where Voc is limited by smaller HOMO-LUMO energy gaps which lower device Fermi levels. However, we have shown that controlling the dye-TiO2 interface is more complex for multiple dyes4. In addition, DSC lifetimes are limited by volatile and corrosive liquid electrolytes, which limit flexible substrate choice to more expensive, inert and non-permeable materials. Liquid electrolytes also complicate device manufacturing and sealing. To date, changing to solid state DSC (ss-DSC) devices has been limited by deficient pore filling by hole transport materials (HTMs) which impairs dye-electrolyte interfaces. With EPSRC support (EP/P030068/1) and working with partners at Glasgow (Prof Graeme Cooke), STFC-Daresbury (Drs Dawn Geatches and Sebastien Metz) and Swansea (Prof Dave Worsley, Drs Cecile Charbonneau and Matt Carnie), we are designing molecules which can self-assemble at the dye-TiO2 and dye-electrolyte interfaces with the aim of achieving rapid, one-step and scalable manufacturing of solid state-DSSC devices
- P.J. Holliman, M.L. Davies, A. Connell, B. Vaca Velasco, T.M. Watson, Chem. Comm., 2010, 46, 7256.
- P.J. Holliman, M. Mohsen, A. Connell, M.L. Davies, K. Al-Salihi, M.B. Pitak, G.J. Tizzard, S.J. Coles, R.W. Harrington, W. Clegg, C. Serpa, O.H. Fontes, C. Charbonneau, M.J. Carnie, J. Mater. Chem., 2012, 22, 13318.
- A. Connell, P.J. Holliman, M.L. Davies, C.D. Gwenin, S. Weiss, M.B. Pitak, P.N. Horton, S.J. Coles, G. Cooke, J. Mater. Chem. A, 2014, 2, 4055.
- P.J. Holliman, K.J. Al-Salihi, A. Connell, M.L. Davies, E.W. Jones, D.A. Worsley, RSC Advances, 2014, 4(5), 2515.