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