Supporting Information

A Solar Cell That Is Triggered by Sun and RainQunwei Tang,* Xiaopeng Wang, Peizhi Yang, and Benlin He

anie_201602114_sm_miscellaneous_information.pdf

Experimental Section

Synthesis of Pt3Ni, Co0.85Se, and Ni0.85Se CEs: The pristine Pt CE was commercially from

Yingkou OPV Tech New Energy Co., LTD. The feasibility of synthesizing Pt3Ni alloy CE was

electrodeposited on thoroughly cleaned ITO-PET flexible substrates by a cyclic voltammetry (CV)

technique. The typical precursor containing 30 mL of 1 mM chloroplatinic acid (H2PtCl6) solution

and 3 mL of 1 mM NiSO4 solutions. The electrodeposition was carried out on a three-electrode

system by scanning in a potential range of -0.6 ~ 0.8 V with a scan rate of 10 mV s-1. After

depositing for seven cycles, the as-prepared CEs were thoroughly rinsed with deionized water and

vacuum dried at 60 oC .

The transparent Co0.85Se and Ni0.85Se alloy CEs were confirmed by following experimental

procedures: A mixing aqueous solution consisting of 2 mM H2SeO3 and 100 mM LiCl was made by

agitating SeO2 ultrafine powders and anhydrous LiCl in deionized water. A mixture comprising of

10 mL of above solution and 10 mL of Co(NO3)2 or Ni(NO3)2 aqueous solution. The deposition of

metal selenide CEs on freshly cleaned ITO-PET substrate was carried out on a conversional

CHI660E setup comprising an Ag/AgCl reference electrode, a CE of platinum sheet, and a working

electrode of ITO/PEN substrate. A cyclic voltammetry mode was applied in a potential range of

−0.9 ~ 1.4 V. The scan rate and scanning number were controlled at 10 mV s−1 and 1 cycle,

respectively.

Synthesis of TiO2 Anodes: A TiO2 colloid was synthesized according to the procedures of our

previous report.[S1] A layer of TiO2 film with an average thickness of 10 μm and active area of 0.25

cm2 was made by a doctor-blade method. Subsequently, the TiO2 film was heated at 60 oC for 5 h

and sensitized by 0.25 mmol dm-3 N719 ethanol solution for 24 h.

Fabrication of rGO Electrode: The rGO film was prepared by filtrating GO colloid prepared

by traditional hummers method, transferred to back side (PET layer) of ITO-PET substrate by a

heat-pressing method (at 40 °C and 0.2 MPa for 10 min), and subsequently reduced with 5 wt% HI

ethanol solution for 10 h.

Assembly of Solar Cell: The bi-triggering solar cell was fabricated by sandwiching redox

electrolyte between a dye-sensitized TiO2 anode and a CE. A Surlyn film (30 μm in thickness) was

utilized to seal the solar cell through hot-pressing. A redox electrolyte consisted of 100 mM of

tetraethylammonium iodide, 100 mM of tetramethylammonium iodide, 100 mM of

tetrabutylammonium iodide, 100 mM of NaI, 100 mM of KI, 100 mM of LiI, 50 mM of I2, and 500

mM of 4-tert-butyl-pyridine in 50 ml acetonitrile.

Electrochemical Characterizations: The electrochemical performances were recorded on a

conventional CHI660E setup comprising an Ag/AgCl reference electrode, a CE of Pt sheet, and a

working electrode of ITO-PET supported CE. The CV curves were recorded in a supporting

electrolyte consisting of 50 mM M LiI, 10 mM I2, and 500 mM LiClO4 in acetonitrile. EIS

measurements were also carried out in a frequency range of 0.1 Hz ~ 105 kHz and an ac amplitude

of 10 mV at room temperature.

Photovoltaic Measurements: The photovoltaic test of the bi-triggering solar cell with an active

area of 0.25 cm2 was carried out by measuring the photocurrent-voltage (J-V) characteristic curves

using a CHI660E Electrochemical Workstation under irradiation of a simulated solar light from a

100 W Xenon arc lamp (XQ-500 W) in ambient atmosphere. The incident light intensity was

controlled at 100 mW cm-2 (calibrated by a standard silicon solar cell). A black mask with an

aperture area of around 0.25 cm2 was applied on the surface of solar cell to avoid stray light

completely.

Other Characterizations: The morphologies of the rGO film were observed on an SU8020

model scanning electron microscope (SEM, SU8020, Hitachi, Japan). X-ray diffraction (XRD)

profile of the rGO film was conducted on a Philips X-ray powder diffractometer with Cu Kα

radiation in the 2θ range of 5 ~ 40º operating at 40 kV accelerating voltage and 40 mA current.

Fourier transform Raman spectrum measurement was performed on a Renishaw inVia Reflex

Raman Spectrometer.

Supporting Table and Figures

Table S1. The corresponding photovoltaic parameters for the flexible DSSCs. η: power conversion

efficiency; Voc: open-circuit voltage; Jsc: short-circuit current density; FF: fill factor.

CEs Voc (V) Jsc (mA cm-2) η (%) FF (%) Irradiation Pt 0.702 12.86 5.98 66.2 front Pt3Ni 0.713 13.82 6.53 66.3 front Co0.85Se 0.701 8.98 4.26 67.7 rear Ni0.85Se 0.696 8.62 4.09 68.2 rear

Figure S1. The structures and components of the bi-triggering solar cells that can be excited by

sunlight and rain: (a) front irradiation, (b) rear irradiation.

-0.6 0.0 0.6 1.2-9

-6

-3

0

3

6

9Ox2, 2I-

3 - 2e = 3I2

Ox1, 3I- - 2e = I-3

Red2, 3I

2 + 2e = 2I-

3

Red1, I-3 + 2e = 3I-

C

urre

nt d

ensi

ty (m

A c

m-2)

Potential (V vs Ag/AgCl)

Pt3Ni alloy CE Pt CE

Eppa

0 5 10 15 20 25 300

5

10

15

20

25

30

Rs

CPE

Rct WRs

CPE

Rct W

Pt3Ni Pt

-Z'' (

ohm

cm

2 )

Z' (ohm cm2)

b

Figure S2. (a) CV curves of Pt and Pt3Ni alloy CEs toward I-/I3- electrolyte recorded at a scan rate

of 50 mV s-1. (b) The Nyquist EIS plots for the symmetric dummy cells with two identical Pt or

Pt3Ni alloy CEs.

1000 1500 2000 2500 3000 3500

2D band

G band

Inte

nsity

(a.u

.)

Raman shift (cm-1)

a D band

5 10 15 20 25 30 35 40

Inte

nsity

(a.u

.)

2theta (degree)

b

Figure S3. (a) Raman spectrum and (b) XRD pattern of the resultant rGO film.

The Raman spectrum of rGO shows two distinct and broad peaks at 1347 and 1594 cm-1, which

are the D and G Raman peaks of graphene, respectively. The peak at 1347 cm-1 (D band, the

breathing mode of k-point phonons of A1g symmetry) is usually associated with vibrations of carbon

atoms with dangling bonds in plane terminations of disordered graphite. The peak at 1594 cm-1 (G

band) corresponds to an E2g mode of graphene and is related to the vibration of sp2-bonded carbon

atoms. The second-order band (2D) is observed around 2930 cm-1. Although the D and 2D bands

can not be used to determine the number of layers, they are useful to investigate electronic defects.

In comparison with pristine graphene, the 2D mode becomes broader, suggesting a higher level of

disorder of the graphene layers and defects.

Figure S4. SEM photographs of rGO film at (a) low and (b) high magnifications.

The stacking architecture and scrolling nature are determined for the rGO film.

0 10 20 30 40 500.00

0.02

0.04

0.06

0.08

0.10C

urre

nt (μ

A)

Time (s)

a

0 20 40 60 80 1000.0

0.2

0.4

0.6

0.8

1.0

Vol

tage

(μV)

Time (s)

b

Figure S5. (a) Current and (b) voltage signals produced by dropping deionized water droplets on

rGO film at an injection velocity of 50 mL h-1. The lateral distance between dropping point and rGO

is 7.46 mm.

Figure S6. The contact angles (a) before and (b) after dropping 0.6 M NaCl droplets.

10 20 30 400

50

100

150

200

Vol

tage

(μV)

Velocity (cm s-1)

Figure S7. The linear relationship between velocity of droplets and induced voltage.

0 5 10 15 20 25 300.0

0.1

0.2

0.30.0

0.2

0.40.0

0.4

0.8

Time (s)

Cur

rent

(μA)

80 mL h-1

50 mL h-1

20 mL h-1

a

0 5 10 15 20 25 300

20

40

0

30

600

40

80

80 mL h-1

50 mL h-1

Time (s)

Pote

ntia

l (μV

)

20 mL h-1

b

Figure S8. (a) Current and (b) voltage signals produced by dropping 1 M NaCl droplets on rGO

film at different injection velocities. The distance between droplets and rGO film is 7.46 mm.

0 5 10 15 20 25 30

0.0

0.2

0.4

0.0

0.2

0.40.0

0.6

1.2

80 mL h-1

50 mL h-1

20 mL h-1

Time (s)

Cur

rent

(μA)

a

0 5 10 15 20 25 300

40

800

30

600

60

120

80 mL h-1

50 mL h-1

20 mL h-1

Time (s)

Pote

ntia

l (μV

)

b

Figure S9. (a) Current and (b) voltage signals produced by dropping 2 M NaCl droplets on rGO

film at different injection velocities. The distance between droplets and rGO film is 7.46 mm.

Supporting References

[S1] S. S. Yuan, Q. W. Tang, B. L. He, L. Men, H. Y. Chen, Electrochim. Acta, 2014, 125, 646.