Download Supporting Information For the discussion of the optical absorption

Supporting Information
For the discussion of the optical absorption spectra of QT (2ML), PTCDI-C8 (2ML) and
PTCDI/QT (2ML/2ML) hetero layers, the experimental details are explained as
supporting information.
The double-beam spectrophotometer (V570, Jasco Co. Ltd.) was used to measure the
transmittance spectra of these organic molecular layers on quartz substrates. The
experimental conditions are shown in Table S1 and Figure S1.
Figure S1: block diagram of spectrophotometer optical system(V570, JASCO).
Table S1: measurement conditions of V570
Scanning Speed
100 nm/min
Spectral Bandwidth
(UV-VIS) 1.0 nm
(NIR) 4.0 nm
Photometric Accuracy
±0.002 Abs (0 to 0.5 Abs)
Photometric Repeatability
±0.001 Abs (0 to 0.5 Abs)
The same batch of quartz substrates were used for the samples and the reference
sample. The samples’ transmittance values were calculated using the reference
transmittance value of quartz, which was taken to be 100%. The reflections (R) from the
organic surfaces are regarded as a variation in the transmittance (approximately 0.5 1%). The R values do not affect the estimation of absorption spectra as shown in this
paper.
The raw data of the transmittance spectra of QT (2ML), PTCDI-C8 (2ML) and
PTCDI/QT (2ML/2ML) hetero layers are shown in Figures S2 to S4;
transmittance [%]
transmittance [%]
100
90
80
200
300
400 500 600
Wavelength [nm]
700
100
90
80
2
800
3
4
5
Photon energy [eV]
6
Figure S2: the raw data of QT (2ML) transmission spectra measured by the V570. The
transmittance [%]
transmittance [%]
x-axes are (left) wavelength and (right) photon energy.
100
90
80
200
300
400
500
600
700
100
90
80
800
2
3
Wavelength [nm]
4
5
6
Photon energy [eV]
Figure S3: the raw data of PTCDI-C8 (2ML) transmission spectra measured by the V570.
transmittance [%]
transmittance [%]
The x-axes are (left) wavelength and (right) photon energy.
100
90
80
70
60
200
300
400
500
600
Wavelength [nm]
700
800
100
90
80
70
60
2
3
4
5
6
Photon Energy [eV]
Figure S4: the raw transmission spectra data of PTCDI-C8 / QT (2ML/2ML) hetero
layers measured by the V570. The x-axes are (left) wavelength and (right) photon
energy
A very weak peak was observed around 2.45 eV. Forker et al. assigned this peak to the
S0-S1 (HOMO-LUMO) transition. A strong absorption peak was reported [17, 18] under
in-situ measurement. However, the transmittance spectrum of our deposited QT 2ML
shows a very weak peak. The molecular orientation of QT is important to this result.
The QT molecules stand vertically on the quartz substrate. The incident direction of our
measurement light probe is perpendicular to the substrate. The QT S0-S1 transition excited by
this irradiation is the optical forbidden transition [18, and 19 in main text and the
density functional theory (DFT) calculation using Gaussian03 B3LYP/6-31G(d)]. We
assigned the absorption above 3.0 eV to the S0-S2 transition, as did Forker. Thus,
Figure2 (in main text) shows the blue contribution area is indicated as the S2 state.
Figure S5: illustrated molecular orbital and electronic state levels of QT for LUMO+1,
LUMO, HOMO, HOMO-1 calculated by Gaussian03 B3LYP/6-31G(d).
However, we do not ignore the possibility atmospheric effects, such as oxidization,
trapping by water, N2 etc., as QT molecules are very sensitive to atmospheric conditions.
Approximately 50 years ago, Y. Maruyama et al. reported the detailed physical
properties of QT thin films and the effect of oxygen on electronic properties [17, 20].
According to these studies, the HOMO level is located around 4.8 eV, which agrees with
the DFT calculation.
Figure S6: the UPS spectra of levels of QT (2ML), PTCDI-C8 (2ML), and QT/PTCDI-C8
(2ML/2ML).
In contrast, the HOMO level is located around 5.9 eV, estimated by UPS measurements
carried out by the authors [Figure S6] and Forker [18]. This result indicates that the
ex-situ measurement reveals the QT HOMO level drops to a lower level or the optical
band-gap expands after exposure to air. In any case, this ex-situ effect is not ignored in
estimating and evaluating the realistic HOMO level after exposure to air [21].
The important point is that the excitation light sources (Eex = 2.54 and 2.78 eV) were
used for the PL and TRPL measurement. The FWHM values of these excitation light
sources are less than 0.01eV. Around 2.54 and 2.78 eV, there are no absorption peaks of
QT or they are very weak compared to the PTCDI layer. Thus, PL and TRPL
measurements enable us to investigate the exciton dynamics of the PTCDI-C8 layer
without the contribution of excitons in the QT layer.