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Ultrafast Heterogeneous Electron Transfer:
The Perylene TiO System2
V. May and L. WangInstitut für Physik
Humboldt-Universität zu Berlinand
S. Ramakrishna and F. WilligHMI, Berlin
Perylene on TiO2
t = 75fs ET -1 -1
w = 357cm , 421cmvib
TiO colloids2
0.5 nm
dye
hw
hw
e
TiO2
Perylen
C(CH )3 3
Cl
Cl
C(CH )3 3
-
- current interest in photoinduced heterogeneous ET V. Sundström (Lund) M. Grätzel (Laussanne)
- besides TiO use of ZnO- and 2
SnO -systems2
- transport and relaxation in the semiconductor conduction band
- back-reactions
- charge injection time of 6 fs for the system alizarin / TiO l2
- study of charge injection after internal conversion, from triplet states, from different conformations,
- theory of nonadiabatic ET well established (Marcus, Jortner)
- ultrafst ET transfer times below 1 ps since 15 eyars search for vibrational coherences
- hetrogeneous ET (perylene / TiO )2
outside a solvent (high vacuum) injection times below 100 fs
Energy level scheme and PES(perylene / TiO )2
Eg
Econ
Ee
Eval
Eg
Econ
Ee
Eval
Eg
Econ
Ee
Eval
diabatic states
|D*>|A> |D>|A>+ -
|D >|A >
Uk
Ue
Ug
2eV
3eVhw=0.1eV
l=0.1-0.3eV
t =75fsET
Uk
Ue
Ug
Ur=0
Ue
Ug
Ur=1
Ur=2
after polynomial expansion
with conduction band continuum
PES
0 20 40 60 80 100time (fs)
0.0
0.2
0.4
0.6
0.8
1.0
leve
l po
pula
tion
0 20 40 60 80 100time (fs)
0.0
0.2
0.4
0.6
0.8
1.0
leve
l po
pula
tion
Change of the Injection Time
V = 0.02 eV V = 0.2 eV
PgPg
Pe
Pe
Pcont
Pcont
Charge injection into the band continuum
Uk
Ue
Ug
Uk
Ue
Ug
l= 0.01eV
l= 0.1eV
l= 0.025 eV
Uk
Uf
Ug
Ue
l= 0.01eV
l= 0.025 eV
l= 0.1eV
Transient Absorption Spectra
t= 10 fs
Laser pulse control of the charge injection process
Uk
Ue
Ug
Uk
Ue
Ug
target state:
displaced vibrational
ground-statein Ug
length of the control pulse:
100f
Bridge Mediated Heterogeneous Electron Transfer
2eV
3eV
hw=0.1eV, l=0.1-0.3eV
Uk
Ue
Ug
U2
U1
0 20 40 60 80 100time (fs)
0.0
0.2
0.4
0.6
0.8
1.0
leve
l po
pula
tion
Pe
P1,2
Pcont
Laser Pulse Control of Bridge Mediated Heterogeneous ET
0 20 40 60 80 100time (fs)
-0.2
0.0
0.2
0.4
0.6
0.8
1.0
leve
l po
pula
tion
0 20 40 60 80 100time (fs)
-0.2
0.0
0.2
0.4
0.6
0.8
1.0
leve
l po
pula
tion
40 60 80 100 120 140time (fs)
-0.2
0.0
0.2
0.4
0.6
0.8
1.0
leve
l po
pula
tion
Pg
P1,2
Pcont
Pcont
Pcont
Pe
Pe
P1,2
P1,2
Pe
Pg
Pg
E(t)
E(t)
E(t)
V =V =V =V =0.05 eVe,1 1,cont e,2 2,cont
V =V =0.05 eVe,1 1,cont
V =V =0.07 eVe,2 2,cont