Background

I did my master's degree at the University of Warwick supervised by James Lloyd-Hughes (2020-2021). During master's studies I worked on developing multi-pixel photoconductive emitters used for generating azimuthally- and radially-polarised terahertz (THz) beams.

Research

The aim of PhD project is to study dynamics of charge-carriers in perovskite nanostructures for optoelectronic applications. I am supervised by Rebecca Milot and James Lloyd-Hughes.

Perovskites are materials possessing chemical formula ABX₃, where A, B are different size cations (A is larger than B) and X is an anion. Mixed organic-inorganic halide perovskites could rival silicon solar cells with less complex solution-based fabrication processing and potentially better performance and versatility, including the use of flexible substrates.

Substitution of A-cation with a long organic spacer of low dielectric constant separates the metal halide sheets forming layered perovskite, in a way similar to 2D materials, e.g. 2D GaAs quantum wells. Layered perovskites possess different properties than its 3D counterpart, such as the quantum confinement of electrons and holes within metal halide layer. This effect allows formation of exciton (bound electron-hole pair) after photon absorption, rather than free electron-hole pair as in 3D perovskite. Layered perovskites could be applied in devices, such as efficient light emitters and stable solar cells, but the investigation of charge carrier properties in these novel materials is necessary.

Fig 1. Crystal structure of 3D and layered perovskite

In my work, I study layered perovskites to understand how organic spacers (A) interact with the inorganic lattice. I employ both optical steady state and time-resolved (pump-probe) spectroscopy to investigate the optoelectronic properties.

Temperature-dependent Structural and Optoelectronic Properties of Layered Perovskite (ThMA₂PbI₄)

Fig 2. Layered perovskite structural changes with temperature and its impact on absorption/photoluminescence emission spectra. Picture taken from J. Phys. Chem. C 2024, 128, 31, 13108-13120

Dependence of Charge-carrier Dynamics on Organic Cation

Fig 2. Schematic diagrams of TEAS and OPTP experiments

Publications

1. Deveikis, J., Giza, M., Walker, D., Liu, J., Wilson, C., Gallop, N. P., Docampo, P., Lloyd-Hughes, J., & Milot, R. L. (2024). Temperature-Dependent Structural and Optoelectronic Properties of the Layered Perovskite 2-Thiophenemethylammonium Lead Iodide. The Journal of Physical Chemistry C, 128(31), 13108–13120.
2. Chopra, N., Deveikis, J., & Lloyd-Hughes, J. (2023). Active THz beam shaping using a one-dimensional array of photoconductive emitters. Applied Physics Letters, 122(6), 61102.
3. Deveikis, J., & Lloyd-Hughes, J. (2022). Multi-pixel photoconductive emitters for the controllable generation of azimuthal and radial terahertz beams. Optics Express, Vol. 30, Issue 24, Pp. 43293-43300, 30(24), 43293–43300.
4. Mosley, C. D. W., Deveikis, J., & Lloyd-Hughes, J. (2021). Precise and accurate control of the ellipticity of THz radiation using a photoconductive pixel array. Applied Physics Letters, 119(12), 121105.

Position: PhD student

Start date: October 2021

Email: Justas.Deveikis@warwick.ac.uk

Office: MAS 3.09