Supplementary information
Enhanced emission of charged exciton-polaritons from colloidal
quantum dots on a SiN/SiO2 slab waveguide
Xingsheng Xu*, Xinyun Li
State Key Laboratory of Integration Optoelectronics, Institute of Semiconductors, Chinese
Academy of Sciences, Beijing 100083, China
* Email: xsxu@semi.ac.cn
The spectra and their tri-Gaussian fits are present in Fig. S1(a) and (b). The spectrum
acquired after a short irradiation time of 2 s is present in Fig. S1(a), and the spectrum acquired
after an irradiation time of 1000 s is present in Fig. S1(b). The spectrum acquired after
irradiation time of 100 s are fitted to a tri-Gaussian function and a bi-Gaussian function, the
corresponding fitted curves are present in Fig. S1(c) and (d), respectively. The spectra at
different irradiation time are compared in Fig. S1 (e). Two dotted lines connect the
wavelength positions of short-wavelength peak and long-wavelength peak, respectively. The
spectra are split and an anticrossing between the two spectral peaks (two modes) is displayed.
The spectra of CQDs on unetched SiN were found to exhibit very few multi-peak
characteristics. The spectrum of CQDs on unetched SiN is shown in Fig. S1(f). This spectrum
contains only one peak, which can be fitted to Gaussian function.
a
1800
100 s
Bi-Gaussian fit
1600
b
1400
100 s
Tri-Gaussian fit
1600
PL intensity (a.u.)
PL intensity (a.u.)
1400
1200
1000
800
600
400
200
1200
1000
800
600
400
200
0
0
540
560
580
600
620
640
540
560
Wavelength (nm)
1.0
Normalized PL intensity
Normalized PL intensity
0.6
0.4
0.2
560
580
600
620
640
620
1000 s
Tri-Gaussian Fit
d
0.8
0.0
540
600
1.0
Experiment, 2s
Tri-exponential fit
c
580
Wavelength (nm)
0.8
0.6
0.4
0.2
0.0
520
640
540
560
580
600
620
Wavelength (nm)
Wavelength (nm)
1500
1400
1000
f
5s
1500
500
1000
0
500
1000
PL intensity (a.u.)
PL intensity (a.u.)
e
100 s
0
500
150 s
0
400
400
200
400 s
0
200
0
520
Experiment
Fit to Gaussian
1200
1000
800
600
400
200
1000 s
0
540
560
580
600
Wavelength (nm)
620
640
540
560
580
600
620
640
Wavelength (nm)
Figure S1 The spectrum of CQDs on SiN/SiO2 with a thickness of 420 nm and
corresponding fitting. (a) BOE etching time of 100 s and bi-Gaussian fit, (b) BOE etching
time of 100 s and tri-Gaussian fit, (c) BOE etching time of 2 s and bi-Gaussian fit, (d) BOE
etching time of 1000 s and bi-Gaussian fit, (e) Comparison of the spectra at different
irradiation time. (f) The spectrum of CQDs on SiN/SiO2 without BOE etching and its
Gaussian fit.
The spectra under different irradiation time fitted into bi-Gaussian function are present in
Fig. S2, the yellow lines are the fitting curves, and the fitted two Gaussian terms are also
shown as dotted-red line and dotted-blue line in corresponding branch figures. The spectrum
with irradiation time 8 s is shown in Fig. S2(a), the spectrum is mainly centered at 585.4 nm,
and there are two weak spectral peaks in both long-wavelength side and short-wavelength
side. With irradiation time increasing to 200 s (Fig. S2(b)), the total PL intensity increases
slightly due to photo-oxidation, the centre wavelength shifts to 581 nm, and the PL intensity
of side peak at short wavelength increased a little compared with that in Fig. S2(a). With
irradiation time increases more to 250 s, it can be found that the main peak blue shifts to
580.5 nm, and the side peak at short-wavelength increased to more than half intensity of the
main peak at 580.5 nm, while the side peak at long-wavelength almost disappeared (Fig.
S2(c)). As irradiation time increases to 500 s in Fig. S2(d), it can be found that the side peak
at short wavelength 553.7 nm increases to similar intensity to that of the main peak at 577.7
nm. The spectrum with irradiation time 570 s is shown in Fig. S2(e), where the side peak at
short wavelength is higher than that at 581 nm.
a
1800
8s
Bi-Gaussian fit
1600
b
200 s
Bi-Gaussian fit
2000
PL intensity (a.u.)
PL intensity (a.u.)
1400
1200
1000
800
600
400
1500
1000
500
200
0
540
560
580
600
620
0
520
640
540
Wavelength (nm)
1800
c
250 s
Bi-Gaussian fit
1600
d
1200
1000
800
600
400
PL intensity (a.u.)
620
500 s
Tri-Gaussian fit
600
400
300
200
0
540
560
580
600
620
520
Wavelength (nm)
500
600
100
200
e
580
500
PL intensity (a.u.)
PL intensity (a.u.)
1400
0
520
560
Wavelength (nm)
540
560
580
600
620
Wavelength (nm)
570 s
Tri-Gaussian fit
400
300
200
100
0
500
520
540
560
580
600
620
Wavelength (nm)
Figure S2 The PL spectra of CQDs on a BOE-etched SiN/SiO2 film for various
irradiation time: (a) 8 s, (b) 200s, (c) 250 s, (d) 500 s. (e) 570 s. (a)-(e) The yellow curved
lines are represent bi-Gaussian fits, the dotted-curves are the Gaussian fits.
16
585
b
Spectral width (nm)
580
14
Cl
Cs
570
12
565
10
560
8
555
0
10
20
30
40
50
60
16.0
15.5
15.0
14.5
14.0
13.5
13.0
12.5
12.0
11.5
11.0
10.5
10.0
9.5
9.0
8.5
8.0
7.5
7.0
70
Wl
Ws
0
10
Irradiation time (m)
d
0.9
0.8
Rl
Rs
0.7
Component ratio
Center wavelength of L-polariton
c
0.6
0.5
0.4
0.3
0.2
0.1
0
10
20
30
40
20
30
40
50
60
70
Irradiation time (m)
50
60
586
L-polariton
S-polariton
585
561
584
583
582
560
27 nm
559
581
558
580
24.1 nm
557
579
25.6 nm
578
556
577
555
576
575
0
70
562
10
20
30
40
50
60
Center wavelength of S-polariton
575
Spectral width (nm)
Center wavelength (nm)
a
554
70
Wavelength (nm)
Irradiation time (nm)
2.236
2.232
2.144
100 meV
El (eV)
2.140
93.7 meV
2.228
2.136 105 meV
2.224
2.132
2.220
2.128
Es (eV)
e
2.148
2.216
2.124
2.212
2.120
0
200
400
600
800
1000
1200
1400
Irradiation time (minute)
Figure S3
The bi-Gaussian fitted parameters of the spectra presented in Fig. S2(a) The
center wavelengths as function of light irradiation time. (b) Spectral widths as function of
light irradiation time. (c) Ratios of the short-wavelength component and the long-wavelength
component to the total emission. (d) Enlarged the center wavelengths as function of light
irradiation time. Cl, Cs, are the center wavelengths of the long-wavelength component and the
short-wavelength component, respectively; Wl, Ws are the spectral widths of the
long-wavelength component and the short-wavelength component, respectively; Rl, Rs are the
ratios of the long-wavelength component and the short-wavelength component to the total
emission, respectively; El, Es are the energy of the long-wavelength component and the
short-wavelength component, respectively. (e) The data presented in Fig. 2(a) in units of meV
instead of nm.
The spectra under different irradiation time are fitted into bi-Gaussian function; the
yellow lines are the fitting curves. The fitted parameters are displayed in Fig. S3. During 68
min, the center wavelength of the short-wavelength component in initial time is around 555
nm, the initial center wavelength of the long-wavelength component around 580 nm, both of
them shift to blue slowly with irradiation time (Fig. S3(a)). Seen from Fig. S3(b), the spectral
width of the long-wavelength component varies from 15.3 to 13.9 nm, while the spectral
width of the short-wavelength component dramatically increases from 7.7 to 14.9 nm. The
ratio of the long-wavelength component to the total component decreases from 0.88 to 0.47,
while the ratio of the short-wavelength component to the total component increases from 0.12
to 0.53 in 68 min (Fig. S3(c)). Correspondingly, the amplitude of the long-wavelength
component decreases dramatically whereas the real amplitude of the short-wavelength
component increases slowly, and the total amplitude (representing the PL intensity) also
dramatically drops in the irradiation time 68 min. The modes as function of the irradiation
time is shown in Fig. S3(d). At initial irradiation time of 1 s, the interval between the
long-wavelength and the short-wavelength mode is 27 nm. As the irradiation time increases to
22 min, the deviation decreases to 24.1 nm. With irradiation time increases to 68 min, the
deviation increases to 25.6 nm. Therefore, two modes of short-wavelength and
long-wavelength strongly couples to each other, as well as exciton and the charged exciton
inter acts with each other.
600
a
555 nm
Bi-exponential fit
500
1000
585 nm
Bi-exponential fit
b
PL intensity (a.u.)
PL intensity (a.u.)
800
400
300
200
600
400
200
100
0
0
5
10
15
20
25
30
35
40
45
0
5
10
Decay time (ns)
15
20
25
30
35
40
45
Decay time (ns)
Figure S4. PL decay at various wavelengths and the fit parameters for the PL decay
fitted to multi-exponential functions (The same point to that of Fig. 4). PL decay at
various wavelengths: (a) 555 nm, (b) 585 nm. The solid black lines represent experimental
results, and the green lines are fitted curves obtained using two-term exponential function.
120
b
600 nm
Tri-exponential fit
200
100
PL intensity (a.u.)
PL intensity (a.u.)
a
610 nm
Tri-exponential fit
80
60
40
150
100
50
20
0
0
0
10
20
30
Decay time (ns)
40
0
10
20
30
Decay time (ns)
40
590 nm
Tri-exponential fit
350
c
700
d
578 nm
Tri-exponential fit
600
PL intensity (a.u.)
PL intensity (a.u.)
300
250
200
150
100
500
400
300
200
100
50
0
0
0
10
20
30
0
40
10
800
570 nm
Tri-exponential fit
f
30
40
560 nm
Tri-exponential fit
350
300
600
PL intensity (a.u.)
PL intensity (a.u.)
e
20
Decay time (ns)
Decay time (ns)
400
200
250
200
150
100
50
0
0
10
20
30
40
0
10
Decay (ns)
550 nm
Tri-exponential fit
200
h
PL intensity (a.u.)
PL intensity (a.u.)
g
20
30
40
Decay time (ns)
150
100
140
540 nm
Tri-exponential fit
120
100
80
60
40
50
20
0
0
0
10
20
30
40
Decay (ns)
Figure S5
0
10
20
30
40
Decay time (ns)
PL decay at various wavelengths (Another point to that of Fig. 4): (a) 610 nm,
(b) 600 nm, (c) 590 nm, (d) 578 nm, (e) 570 nm, (f) 560 nm, (g) 550 nm, (h) 540 nm. The
black hollow-circle lines represent experimental results, and the green lines are fitted curves
obtained using two-term exponential function.
26
Exciton lifetime
24
7
b
22
Lifetime of trion (ns)
Lifetime of exciton (ns)
a
20
18
16
14
12
Trion lifetime
6
5
4
3
10
2
8
530
540
550
560
570
580
590
600
610
530
620
540
550
Mult-exciton lifetime
1.8
0.7
d
1.6
1.2
1.0
0.8
0.6
580
590
600
610
620
0.6
Exciton
Multi-exciton
Trion
0.5
0.4
0.3
0.2
0.4
0.1
0.2
0.0
530
540
550
560
570
580
590
600
610
620
0.0
530
540
550
560
570
580
590
600
610
Wavelength (nm)
Wavelength (nm)
e
570
1.4
Component ratio
Lifetime of multi-exciton
c
560
Wavelength (nm)
Wavelength (nm)
0ns
10 ns
1.0
PL intensity
0.8
0.6
0.4
0.2
0.0
540
550
560
570
580
590
600
610
620
Wavelength (nm)
Figure S6
Fit parameters for the PL decay at various wavelengths fitted to
tri-exponential functions (The same point to that of Fig. 4). (a) The lifetimes for exciton
emission, (b) The lifetimes for charged-exciton emission, (c) The lifetimes for multi-exciton
emission, (d) The component ratios from the tri-exponential fitting of PL decay at various
wavelengths. (e) The PL spectra at various delay time determined from the PL decay curves at
various wavelengths.
As PL decays at different wavelength from CQDs in another position of SiN/SiO2 are
displayed in Fig. S5. The PL decays are fitted to three-termed exponentials and the fitted
parameters are collected in Fig. S6. As wavelength changing in the range of 535 nm to 610
nm, the lifetimes for the long-lifetime term are in the range of 9.11 ns and 24.08 ns, the
lifetime for the middle lifetime term are in the range 2.08 ns and 7 ns, this term is attributed to
exciton emission; this term is attributed to charged-exciton emission; while the lifetime for the
short-lifetime term is in the range of 0.15 ns and 1.74 ns, this terms is attributed to
multi-exciton emission. In the wavelength ranging from 535 nm and 580 nm, the
corresponding ratios of the charged-exciton term are in the range 0.47 and 0.62. The ratios of
the multi-exciton components to the total component are 0.12 and 0.40, while the ratios of the
exciton component are 0.16 and 0.39. Moreover, the curves of all the parameters including,
lifetimes and component ratios as function of the wavelength, fluctuated with the wavelength.