electron dynamics in transition metal oxides geoff …...electron dynamics in transition metal...

•  Applications in photovoltaics, photochemistry and catalysis.

•  Large band gap of a few electron volts. ü  TiO2 band gap: ~3 eV ü  Photocatalysis and light harvesting

Time-resolved photoelectron spectroscopy with XUV. •  Dynamics of conduction band (CB)

and valence band (VB) •  Selective excitations

ü  VBàCB transition ü  Polaron excitation

Electron dynamics in transition metal oxides Geoff Thornton, UCL Time Resolved Photoemission

Electron dynamics in transition metal oxides Geoff Thornton, UCL Time Resolved Photoemission

1.0

0.8

0.6

0.4

0.2

0.0

-0.2

Inte

nsity

(a.u

.)

-3 -2 -1 0 1E-EF (eV)

x5

No pump Delay 50 fs Difference

Defect state excitation •  Polaron: photon-assist hopping in a

time scale of 50 fs

defect states

YZhang,DPayne,C.L.Pang,CCacho,R.T.Chapman,ESpringate,H.H.Fielding,G.Thornton,J.Phys.Chem.Lett.2019,10,5265

Electron dynamics in transition metal oxides Geoff Thornton, UCL Time Resolved Photoemission

Future Prospects: •  C,N,O core level photoemission to investigate water chemistry,

photodegradation on transition metal oxides—EuXFEL up to 1 keV •  Eg Hybrid perovskites, element-specific recombination paths and charge

transfer to electron and hole collectors

•  Time resolved photoelectron diffraction to follow electron path following pump pulse

•  Tender X-rays (4 keV) and HAXPES measurements at liquid solid interfaces for hybrid perovskite/ TiO2 interfaces