Supplementary Information
Ultrasensitive PbS quantum dot sensitized InGaZnO hybrid photoinverter for near-infrared detection and imaging with high photogain
Do Kyung Hwang1,2† ★ , Young Tack Lee1†, Hee Sung Lee3, Yun Jae Lee1,4, Seyed Hossein
Shokouh3, Ji-hoon Kyhm1, Junyeong Lee3, Hong Hee Kim1, Tae-Hee Yoo1, Seung Hee Nam3,
Dong Ick Son5, Byeong-Kwon Ju4, Min-Chul Park6, Jin Dong Song1, Won Kook Choi2,7★, and
Seongil Im3★
1
Center for Opto-Electronic Materials and Devices
Post-Silicon Semiconductor Institute
Korea Institute of Science and Technology (KIST), Seoul 02792, Korea
2
Department of Nanomaterials and Nano Science
Korea University of Science and Technology (KUST), Daejun 34113, Korea
3
Institute of Physics and Applied Physics
Yonsei University, Seoul 03722, Korea
4
Display and Nanosystem Laboratory
School of Electrical Engineering, Korea University, Seoul 02841, Korea
5
Soft Innovative Materials Research Center
Korea Institute of Science and Technology (KIST), Jeonbuk 55324, Korea
6
Sensor System Research Center
Korea Institute of Science and Technology (KIST), Seoul 02792, Korea
7
Materials and Life Science Research Division
Korea Institute of Science and Technology (KIST), Seoul 02792, Korea
†
These authors contributed equally to this work.
★e-mail:
dkhwang@kist.re.kr; wkchoi@kist.re.kr; semicon@yonsei.ac.kr
1
Contents
1. Optical properties of colloidal PbS solution and description of ligand exchange. (Fig. S1)
2. Device performance of PbS-EDT (processed with AN)/IGZO transistor and ligand process &
CYTOP Passivation effects on electrical properties of IGZO transistor. (Fig. S2)
3. Optical power of a light source. (Fig. S3)
4. Phototransistor device characteristics. (Fig. S4 and S5)
5. Photo-excited effective charge density. (Fig. S6)
6. Gate dependent photoresponsivity, noise power density, noise equivalent power, and specific
detectivity, and photosensitivity. (Fig. S7-S9)
7. Dependence of photoresponse on illumination intensity (Fig. S10)
8. Temporal photocurrent response (Fig. S11)
9. NIR (1300 nm) imager (Fig. S12 and Fig. S13)
2
Figure S1. Absorption and photoluminescence spectra of collidal PbS QDs solution dispersed in
toluene (Nanodot® - PbS 1300, purchased from QD SOLUTION Co.).
3
Ligand exchange process effect on optical properties
The optical properties varied significantly with the capping ligands, as shown in the Fourier
transform infrared (FTIR) spectra of Fig. 1c and visible-near infrared (Vis-NIR) absorption
spectra of Fig. 1d. The pristine PbS-OA film shows strong carboxylate (COO-) symmetric and
asymmetric stretching vibration absorption band at between 1400 and 1550 cm-1 and very intense
C-H stretching vibration absorption band at between 2800 and 3000 cm-1 in the FTIR spectra.
For the EDT-treated films processed with methanol (MO) and acetonitrile (AN) solvents, the
intensities of above vibration absorption bands were substantially reduced, indicating the absence
of OA ligands. The Vis-NIR absorption spectra are also consistent with the FTIR spectra. Based
on the PbS QD diameter of 4 - 5 nm estimated from HRTEM results, the quantum-confined
energy bandgap can be calculated to be between 0.9 and 1.06 eV (the corresponding wavelengths
at 1380 and 1170 nm) by the formula proposed by Moreels et al.1,2 The first exciton peak at 1320
nm (corresponding energy of 0.94 eV) was observed in the colloidal PbS solution (see above Fig.
S1) and this optical transition matches the calculated quantum-confined energy bandgap. In the
PbS-OA film, the exciton peak at 1380 nm was red-shifted by about 60 nm relative to its position
when in solution state, which is a common feature resulting from the aggregation when in solid
state. The EDT-treated films exhibited more red-shifted exciton peaks at 1400 nm (Processed
with the AN solvent) and 1410 nm (Processed with the MO solvent). In addition, the relative
intensity of absorption bands was observed to be in the order: PbS-OA < PbS-EDT (AN) < PbSEDT (MO). The red-shifted first exciton peaks and their increased relative intensities in
absorption spectra suggest that the EDT treatment enhances electronic coupling (delocalization
of electron and hole wavefunctions) arising from the reduced interparticle distance (enhanced
interparticle interaction)1,3 and the MO solvent is likely to be more efficient for the EDT ligand
4
exchange process than the AN solvent, which gives a significant impact on the photoelectrical
performance.
1.
Tang, J. et al. Quantum Dot Photovoltaics in the Extreme Quantum Confinement
Regime: The Surface-Chemical Origins of Exceptional Air- and Light-Stability. ACS
Nano 4, 869-878 (2010).
2.
Zhang, D. Y. et al. Understanding Charge Transfer at PbS-Decorated Graphene Surfaces
toward a Tunable Photosensor. Adv. Mater. 24, 2715-2720 (2012).
3.
Tang, J. et al. Colloidal-quantum-dot photovoltaics using atomic-ligand passivation. Nat.
Mater. 10, 765-771 (2011).
5
b
30
20
10
500
W/L = 1000 m/ 50 m
VDS = 0 to 20 V
400
IDS (A)
10-3
W/L = 1000 m/ 50 m
10-4
VDS = 20 V
10-5
PbS-EDT
10-6 (processed
10-7
AN)/IGZO
10-8
10-9
10-10
10-11
10-12
10-13
-20
-10
0
IDS1/2 (A)1/2
IDS (A)
a
Step = 5 V
PbS-EDT
(processed
AN)/IGZO
300
200
100
10
0
20
0
0
5
10
VGS (V)
VDS = 30 V
10-5
10-6
IGZO
20
Prestine
PbS-EDT
CYTOP coating
10-7
10
W/L = 1000 m/ 150 m
VDS = 30 V
d
-8
10
10-9
IGZO
300
IDS (A)
10
IDS (A)
400
10-3 W/L = 1000 m/ 150 m
-4
20
VDS (V)
IDS1/2 (A)1/2
c
15
200
Prestine
PbS-EDT
CYTOP coating
100
10-10
10-11
-20
-10
0
10
VGS (V)
20
0
30
0
0
5
10
15
20
25
30
VDS (V)
Figure S2. Representative (a) transfer and (b) output characteristics of PbS-EDT (processed
from AN)/IGZO TFTs (W/L= 1000 μm/50 μm) measured in a dark air ambient. Representative
(c) transfer and (d) output characteristics of IGZO TFTs before and after PbS-EDT treatment
(processed MO), and with further CYTOP passivation (W/L= 1000 μm/150 μm). PbS-EDT
treatment induced positive shifts of turn-on and threshold voltages. After CYTOP passivation,
these shifts were a little recovered.
6
2
Optical power (mW/cm )
0.6
0.4
0.2
0.0
1.0
1.5
2.0
Photon Energy (eV)
Figure S3. The illumination intensities of a light source of 500 W Hg(Xe) arc lamp.
7
-20
-10
Dark
1500
1400
1300
1200
1100
1000
900
800
700
0
10
20
c
10-3 W/L = 1000 m/ 50 m
10-4 VDS = 20 V
10-5
PbS-OA/IGZO
10-6
-7
10
10-8
10-9
10-10
10-11
10-12
-20
VGS (V)
-10
0
Dark
1500
1400
1300
1200
1100
1000
900
800
700
10
IDS (A)
b
10-3 W/L = 1000 m/ 50 m
10-4 VDS = 20 V
10-5
IGZO
10-6
-7
10
10-8
10-9
10-10
10-11
10-12
IDS (A)
IDS (A)
a
20
10-3 W/L = 1000 m/ 50 m
10-4 VDS = 20 V
10-5
PbS-EDT/IGZO
10-6
-7
10
10-8
10-9
10-10
10-11
10-12
-20
-10
VGS (V)
0
Dark
1500
1400
1300
1200
1100
1000
900
800
700
10
20
VGS (V)
Figure S4. Dark and photo-induced transfer curves of (a) IGZO, (b) PbS-OA/IGZO, and (c)
PbS-EDT (Processed with MO)/IGZO TFTs under monochromatic lights with spectral range of
IDS (A)
700 - 1500 nm (wavelength interval of 100 nm).
10-3 W/L = 1000 m/ 50 m
10-4 VDS = 20 V
10-5
10-6
10-7
10-8
10-9
10-10
10-11
10-12
-20
-10
0
Dark
1500
1400
1300
1200
1100
1000
900
800
700
10
20
VGS (V)
Figure S5. Dark and photo-induced transfer curves (plot every 100 nm interval) of PbS-EDT
(processed from AN)/IGZO TFTs under monochromatic lights with spectral range of 700 - 1500
nm.
8
Absorption (a. u.)
11
-2
Qeff/q (10 cm )
8
6
4
2
1440 nm (0.86 eV)
0
800
1000
1200
1400
Wavelegth (nm)
Figure S6. The photo-excited effective charge density (Qeff) plot of the PbS-EDT (processed
with MO)/IGZO phototransistor indicates that the approximate optical energy bandgap is
estimated to be 0.86 eV for the PbS-EDT QDs. This is consistent with the absorption spectra of
the PbS-EDT film.
9
4
10
2
R (A/W)
10
0
10
1500
1400
1300
1200
1100
1000
900
800
700
-2
10
-4
10
-20
-10
0
10
20
VGS (V)
Figure S7. Plots of photoresponsivity (R) as a function of gate voltage under monochromatic
lights with spectral range of 700 - 1500 nm.
10
-16
10
f = 10 Hz
2
-1
Noise power spectral density (A /Hz )
b
a
VG= 20 V
VG= 10 V
VG= 5 V
VG= -20 V
-18
10
-20
10
-22
10
-24
10
-26
10
-20
-10
0
10
20
VGS (V)
10
d
-12
10
-14
10
10
1500
1400
1300
1200
1100
1000
900
800
700
*
-10
10
-20
10
10
8
10
1500
1400
1300
1200
1100
1000
900
800
700
6
10
4
-16
10
14
10
12
-8
D (Jones)
NEP (W Hz
-1/2
10
)
-6
c
-10
0
VGS (V)
10
20
10
-20
-10
0
10
20
VGS (V)
Figure S8. (a) Snapshot of noise spectrum obtained from Advantest R9211B digital spectrum
analyzer as function of selected gate voltage (VG = 20, 10, 5, and -20 V). (b) Gate dependent
noise power spectral density. (c) Noise equivalent power (NEP) and (d) specific detectivity (D*)
as a function of gate voltage under monochromatic lights with spectral range of 700 - 1500 nm.
11
5
Photosensitivity
10
3
10
1
10
1500
1400
1300
1200
1100
1000
900
800
700
-1
10
-20
-10
0
10
20
VGS (V)
Figure S9. Plots of photosensitivity as a function of gate voltage under monochromatic lights
with spectral range of 700 - 1500 nm.
12
7
b
5.97 pW
19.9 PW
38.8 PW
59.7 PW
0.19 nW
0.29 nW
0.62 nW
14
10
12
10
5.97 pW
19.9 PW
38.8 PW
59.7 PW
0.19 nW
0.29 nW
0.62 nW
10
10
*
10
6
10
5
10
4
10
3
10
2
10
1
10
0
10
-1
10
-2
10
-3
10
-4
10
-20
D (Jones)
R (A/W)
a
8
10
6
-10
0
10
10
-20
20
-10
d
-6
10
20
-14
10
VG = 20 V
-1/2
)
10
NEP (W Hz
NEP (W Hz
-1/2
)
-8
10
VGS (V)
VGS (V)
c
0
-10
10
-12
10
-14
10
5.97 pW
19.9 PW
38.8 PW
59.7 PW
0.19 nW
0.29 nW
0.62 nW
-15
10
-16
10
-20
-10
0
10
20
VGS (V)
-11
10
-10
10
-9
10
Light Power (W)
Figure S10. Plots of (a) R, (b) D*, and (c) NEP as a function of gate voltage under 1000 nmwavelength light illumination with different optical powers ranged from 5.97 pW and 0.62 nW.
(d) Irradiance-dependent NEP at VG = 20 V.
13
a
b
-8
4.0x10
Light on
-8
3.0x10
-8
IDS(A)
3.0x10
IDS(A)
-8
4.0x10
-8
2.0x10
-8
1.0x10
fast = 0.57 sec
-8
1.0x10
0.0
Light off
0
100
200
slow = 9.55 sec
-8
2.0x10
Experimental result
Fitting Curve
0.0
300
400
500
Time (s)
600
0 10 20 30 40 50 60 70 80 90 100
Time (s)
Figure S11. Temporal photocurrent response of the device under monochromic NIR light with
wavelength of 1000 nm (0.34 mWcm-2).
14
LED light source
: (SMBB1300-1100)
IR Shadow mask (KIST)
1. Resistor-load inverter part
CYTOP passivation
External resistor
PbS QDs
Source
Drain
IGZO
Gate insulator
100 MΩ
Global gate
VIN
(2V)
VDD
(5V)
Substrate
VOUT = IN+
Moving stage (x-z plane)
: VEXTA(C7214-9015-1)
3. Measurement part
2. Voltage follower part
-10V
National Instrument
(PXI1033 & PXI4132)
OP-AMP
(OP07CP)
VCC
VCC- IN+ IN-
IN+
OUT VCC+
+
OUT
-
Final signal (V)
National Instrument, (Labview)
+10V
Figure S12. Schematic of the NIR imaging experimental setup. The NIR imaging experimental
setup consist of three parts: 1) PbS/IGZO hybrid phototransistor based resistive-load inverter part
as NIR imager, 2) voltage follower part for transmission of output signals, and 3) measurement
part for image acquisition.
15
VOUT
VIN
1300 nm
LED source
VDD
100 MΩ
Detect
unit
Vis-NIR filter
< 1200nm
(Si wafer)
1.5V
IR
Shadow
mask
(Metal)
Figure S13. Schematic illustration of NIR imaging process with Si wafer used as Vis-NIR filter
(cut-off below 1200 nm-wavelength) and measured image acquired with our NIR (1300 nmwavelength) imager.
16