Latest Publications

Ultrafast photo-induced phonon hardening due to pauli blocking in $MAPbI_3$ single-crystal and polycrystalline perovskites Xia et al. J. Phys-Mater., 4:044017 (Oct 2021) [ pdf ][ DOI:10.1088/2515-7639/ac22b9 ] We observed the shift of phonon modes in thin file and single crystals MAPbI3 that occurs when the materials are optically excited. We observe an ultrafast Pauli blocking effect with leads to phonon hardening / blue-shifting.	Hot electron cooling in InSb probed by ultrafast time-resolved terahertz cyclotron resonance Xia et al. Phys. Rev. B, 103:245205 (Jun 2021) [ pdf ][ DOI:10.1103/PhysRevB.103.245205 ] We develop and apply the technique of time resolved cyclotron resonance to observe electron cooling in the narrow bandgap semiconductor indium antimonide and find excellent agreement with first principles GW calculations.	Limits to electrical mobility in lead-halide perovskite semiconductors Xia et al. J. Phys. Chem. Lett., 12:3607-3617 (Apr 2021) [ pdf ][ DOI:10.1021/acs.jpclett.1c00619 ] We measure THz photoconductivity of single crystals and thin films of the prototypical metal halide perovskite MAPbI3. This direct comparison combined with DFT calculations allows us to study the influence of grain boundaries on charge-carrier scattering, and hence mobility.
Three-dimensional cross-nanowire networks recover full terahertz state Peng et al. Science, 368:510--513 (May 2020) [ pdf ][ DOI:10.1126/science.abb0924 ] We have developed a new nanowire-based THz sensor that recovers the full state of THz pulses.	Trap states, electric fields, and phase segregation in mixed-halide perovskite photovoltaic devices Knight et al. Adv. Energy Mater., 10:1903488 (Mar 2020) [ pdf ][ DOI:10.1002/aenm.201903488 ]	Light absorption and recycling in hybrid metal halide perovskite photovoltaic devices Patel et al. Adv. Energy Mater., 10:1903653 (Mar 2020) [ pdf ][ DOI:10.1002/aenm.201903653 ] We use vapour co-deposition to control precisely the thickness of perovskite films, and study the effect of light management in thin film solar cells