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SUPPLEMENTARY INFORMATIONDOI: 10.1038/NMAT4150

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1

Supplementary Information

Giant Switchable Photovoltaic Effect in Organometal Trihalide Perovskite Devices

Zhengguo Xiao1,2†, Yongbo Yuan1,2†, Yuchuan Shao 1,2†, Qi Wang,1,2 Qingfeng

Dong,1,2 Cheng Bi1,2, Pankaj Sharma2,3, Alexei Gruverman2,3 and Jinsong Huang1,2 *

1Department of Mechanical and Materials Engineering, University of Nebraska-Lincoln,

Lincoln, Nebraska 68588-0656, USA. 2Nebraska Center for Materials, Nanoscience,

University of Nebraska-Lincoln, Lincoln, Nebraska 68588-0298, USA. 3Department of Physics

and Astronomy, University of Nebraska-Lincoln, Lincoln, Nebraska 68588-0299, USA

*Correspondence to: [email protected]

0.00 0.05 0.10 0.15-10

-8

-6

-4

-2

0

Cur

rent

den

sity

(mA

/cm

2 )

Voltage (V)

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SUPPLEMENTARY INFORMATION DOI: 10.1038/NMAT4150

2

Figure S1. J-V characteristics of the as-prepared vertical structure devices with the structure of

(ITO)/poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) /Perovskite (300

nm) /Au. Scanning rate was 0.14 V/s and the scanning direction was labeled in the figure.

Fig. S1 shows current density (J)-voltage (V) characteristics of the as-prepared device with

300 nm perovskite layers. The arrow in the figure depicts the scanning direction. Here, the

scanning direction for J-V characteristics was from zero to positive voltage to rule out the

possibility for a high JSC caused by the un-intentional poling process during device test. It’s

impressive that the device with gold electrode, which usually serves as a contact for hole-only

device, has a high short current density (JSC) of 8.2 mA/cm2. The result indicates the junction has

been partially formed before poling. The reason for junction formation before poling should be

related to different interface structures between perovskite/PEDOT:PSS and perovskite/Au

contacts, because the JSC from the as-fabricated device using gold as both anode and cathode is

much smaller.

3

Figure S2. Dark current (a) and photocurrents (b) of the vertical structure devices with the

structure of ITO/PEDOT:PSS /Perovskite (300 nm)/Au tested under different scanning rate and

directions.(c-d) VOC (c) and JSC statistics based on five devices with different scanning rates from

0.05 V/s to 0.25 V/s. Forward scanning refers scanning from negative to positive bias. In all the

measurements, ITO was connected as the cathode and Au was connected as the anode.

Fig. S2 shows the dark current and photocurrent hysteresis of the same ITO/PEDOT:PSS

/Perovskite (300 nm)/Au vertical structure device with different scanning rates and directions.

The arrows in the figure depict the bias scanning directions. A large memristive effect from the

-3 -2 -1 0 1 2 3

-200

-100

0

100

200

300

400 0.05 V/s 0.10 V/s 0.25 V/s

Cur

rent

den

sity

(mA/

cm2 )

Voltage (V)-3 -2 -1 0 1 2 3

-200

-100

0

100

200

C

urre

nt d

ensi

ty(m

A/cm

2 )

Voltage (V)

0.05 V/s 0.10 V/s 0.25 V/s

a b

0.05 0.10 0.15 0.20 0.25

-0.8

-0.6

-0.40.4

0.6

0.8

V OC (V

)

Scanning rate (V/s)0.05 0.10 0.15 0.20 0.25

-25

-20

-15

15

20

25

J SC (m

A/cm

2 )

Scanning rate (V/s)

c d

Forward scanning

Reverse scanning

Forward scanning

Reverse scanning





2

Figure S1. J-V characteristics of the as-prepared vertical structure devices with the structure of

(ITO)/poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) /Perovskite (300

nm) /Au. Scanning rate was 0.14 V/s and the scanning direction was labeled in the figure.

Fig. S1 shows current density (J)-voltage (V) characteristics of the as-prepared device with

300 nm perovskite layers. The arrow in the figure depicts the scanning direction. Here, the

scanning direction for J-V characteristics was from zero to positive voltage to rule out the

possibility for a high JSC caused by the un-intentional poling process during device test. It’s

impressive that the device with gold electrode, which usually serves as a contact for hole-only

device, has a high short current density (JSC) of 8.2 mA/cm2. The result indicates the junction has

been partially formed before poling. The reason for junction formation before poling should be

related to different interface structures between perovskite/PEDOT:PSS and perovskite/Au

contacts, because the JSC from the as-fabricated device using gold as both anode and cathode is

much smaller.

3

Figure S2. Dark current (a) and photocurrents (b) of the vertical structure devices with the

structure of ITO/PEDOT:PSS /Perovskite (300 nm)/Au tested under different scanning rate and

directions.(c-d) VOC (c) and JSC statistics based on five devices with different scanning rates from

0.05 V/s to 0.25 V/s. Forward scanning refers scanning from negative to positive bias. In all the

measurements, ITO was connected as the cathode and Au was connected as the anode.

Fig. S2 shows the dark current and photocurrent hysteresis of the same ITO/PEDOT:PSS

/Perovskite (300 nm)/Au vertical structure device with different scanning rates and directions.

The arrows in the figure depict the bias scanning directions. A large memristive effect from the

-3 -2 -1 0 1 2 3

-200

-100

0

100

200

300

400 0.05 V/s 0.10 V/s 0.25 V/s

Cur

rent

den

sity

(mA/

cm2 )

Voltage (V)-3 -2 -1 0 1 2 3

-200

-100

0

100

200

Cur

rent

den

sity

(mA/

cm2 )

Voltage (V)

0.05 V/s 0.10 V/s 0.25 V/s

a b

0.05 0.10 0.15 0.20 0.25

-0.8

-0.6

-0.40.4

0.6

0.8

V OC (V

)

Scanning rate (V/s)0.05 0.10 0.15 0.20 0.25

-25

-20

-15

15

20

25

J SC (m

A/cm

2 )

Scanning rate (V/s)

c d

Forward scanning

Reverse scanning

Forward scanning

Reverse scanning





4

devices was observed because the dark- and photocurrent curves have a strong dependence on

the scanning history.

Figure S3. a-b, Dark current of the ITO/PEDOT:PSS/Perovskite (300 nm)/Au vertical structure

devices during positive and negative poling process, c, Dynamic poling process of the

ITO/PEDOT:PSS/Perovskite/Au vertical structure device with 1,015 nm thick perovskite layer

using -1.0 V pulse.

As shown in Fig. S3 a-b, in the positive poling (+2.5 V) process, the current density is very

small at the beginning of the poling process, which corresponds to the reverse-biased dark

current of the n-i-p structure device (region I). The current increased quickly with increased

0 50 100 150 200 250-1.6

-1.2

-0.8

-0.4

0.0

0.4

0.8

Measured device VOC

11.3 s8.4 s4.2 s1.5 s0.2 s

Vol

tage

(V)

Time (s)

Accumulated poling time

Poling bias= -1V

0 20 40 60 80 1000

20

40

60

+2.5 V poling

Cur

rent

den

sity

(mA/

cm2 )

Time (s)0 10 20 30 40 50 60

-80

-60

-40

-20

0

-2.5 V poling

Cur

rent

den

sity

(mA/

cm2 )

Time (s)

a b

- +- + + - + -

c

5

poling time, and a current peak showed up, which should be due to the ion motion in the

perovskite under reverse bias (region II). The current begun to reduce after tens of seconds

poling due to the depletion of easily mobile ions, and the current came to a plateau (region III)

with high current density, indicating the perovskite film was switched to p-i-n structure and the

device worked at forward bias with a large injection current. The negative poling showed a short

poling time than positive poling, indicating the non-symmetrical composition/morphology

profile along the vertical direction.

Fig. S3c shows the dynamic poling process of the device with 1,015 nm thick perovskite

layer. Here a train of -1.0 V pulses with different width were applied on the device, after which

the VOC of the device was measured. The accumulated poling time, poling bias and measured

device VOC were also marked in the figure. As shown in the figure, the device was switched after

11.3 s accumulated poling.

10 100 1000

-1.0

-0.5

0.0

0.5

1.0

JSC (After negative poling) JSC (After positive poling)

Nor

mal

ized

JS

C (a

.u.)

Time (h)





6

Figure S4. The stability test of short circuit current for the ITO/PEDOT:PSS/Perovskite (300

nm)/Au vertical structure device after positive and negative poling for 20 s at ±2 V. (The JSC

were normalized by the value measured 24 h after the fabrication of the device (18.2 mA/cm2 and

-19.0 mA/cm2).

Fig. S4 shows the stability test result of the short circuit photocurrent for devices after

positive and negative poling. The photocurrent direction after poling remained unchanged after

two months. Two devices were negatively and positively poled, respectively, under a steady bias

of 2.5 V for about ten seconds. After that, the devices were kept under ambient illumination in a

glove box and no further poling was applied during the test. In order to eliminate the influence of

scanning voltage, we only test the JSC to identify the stability of current direction. As illustrate in

the figure, the JSC for both directions changed a small rate of ~10% for the first 100 hours. It’s

amazing no obvious reduction was identified for device with negative current after 1000 hours.

7

Figure S5. Performance variation of the ITO/PEDOT:PSS/Perovskite (300 nm)/Au vertical

structure devices. Scanning rate was 0.14 V/s. Photovoltaic performance statistics of the vertical

structure devices. The vertical structure devices were poled at 6 V/µm for 20 s. The

photocurrents were measured under 1 sun illumination at a sweep rate of 0.14 V/s, b,

Distribution of the photovoltaic performance of vertical structure devices in the JSC-VOC

coordinate. c, VOC distribution of the poled vertical structure devices; d, JSC distribution of the

poled vertical structure device;

It is found that there is a large variation for the performances of the ITO/PEDOT:PSS

/Perovskite (300 nm)/Au vertical structure devices. Some devices showed larger photocurrent

-1.0 -0.5 0.0 0.5 1.0-9

-6

-3

0

3

6

9

12

Positive polingCur

rent

den

sity

(mA

/cm

2 )

Voltage (V)

Negative poling

-1.0 -0.5 0.0 0.5 1.0-20-15-10-505

101520

Positive poling

Negative poling

J SC (

mA

/cm

2 )

VOC (V)

20 10 0 -10 -2001234567

Positive poling

Cou

nt

Negative poling

JSC (mA/cm2)-1.0 -0.5 0.0 0.5 1.002468

1012 Negative poling

C

ount

Positive poling

VOC (V)

a b

dc





8

while some others showed larger VOC. Fig. S5 shows one device with large switchable

photovoltage between 0.87 V and -0.75 V.

Figure S6. Switchable photovoltaic effect of the ITO/PEDOT:PSS/Perovskite (300 nm)/Au

vertical structure devices with different perovskite materials, a, CH3NH3PbI3-xClx, b,

HC(NH2)2PbI3 and c, CH3NH3PbBr3. The devices were scanned between ±2.5 V at a scanning

rate of 0.14 V/s.

-0.6 -0.4 -0.2 0.0 0.2 0.4 0.6

-20-15-10-505

101520

Positive poling

Negative poling

MAPbIxCl3-x

Cur

rent

den

sity

(mA/

cm2 )

Voltage (V) -0.4 -0.2 0.0 0.2 0.4 0.6

-15-10-505

101520

Positive poling

Negative poling

HC(NH2)2PbI3

Cur

rent

den

sity

(mA/

cm2 )

Voltage (V)

-0.4 -0.2 0.0 0.2 0.4

-6

-3

0

3

6

9

MAPbBr3

Positive poling

Negative poling

Cur

rent

den

sity

(mA/

cm2 )

Voltage (V)

a

c

b

9

In order to confirm the ion drift induced photovoltaic switching mechanism, we examined other

three organolead trihalide perovksite materials, CH3NH3PbI3-xClx, HC(NH2)2PbI3 and

CH3NH3PbBr3 (Fig. S6). It is found all the devices with these materials as active layers showed

field switchable photovoltaic behavior.

Figure S7. Switchable photovoltaic effect of the ITO/PEDOT:PSS/Perovskite (300 nm)/Metal

vertical structure devices with different metal contacts of Pt, Ni and Ga. The devices were

scanned between ±2.5 V at a scanning rate of 0.14 V/s.

In order to examine whether gold is required for the switchable OTP devices, we tested other

metals like aluminum (Al), silver (Ag), platinum (Pt), gallium (Ga) and nickel (Ni) using the

-1.0 -0.5 0.0 0.5 1.0-20.0-15.0-10.0-5.00.05.0

10.015.020.0

Negative poling

Pt cathode

Positive poling

Cur

rent

den

sity

(mA

/cm

2 )

Voltage (V)-1.0 -0.5 0.0 0.5 1.0

-6

-4

-2

0

2

4

6

Negative poling

Positive Poling

Cur

rent

den

sity

(mA/

cm2 )

Voltage (V)

Ni cathode

-0.4 -0.2 0.0 0.2 0.4 0.6-8.0-6.0-4.0-2.00.02.04.06.0

Negative poling

Ga cathode

Positive poling

Cur

rent

den

sity

(mA

/cm

2 )

Voltage (V)

a b

c





8

while some others showed larger VOC. Fig. S5 shows one device with large switchable

photovoltage between 0.87 V and -0.75 V.

Figure S6. Switchable photovoltaic effect of the ITO/PEDOT:PSS/Perovskite (300 nm)/Au

vertical structure devices with different perovskite materials, a, CH3NH3PbI3-xClx, b,

HC(NH2)2PbI3 and c, CH3NH3PbBr3. The devices were scanned between ±2.5 V at a scanning

rate of 0.14 V/s.

-0.6 -0.4 -0.2 0.0 0.2 0.4 0.6

-20-15-10-505

101520

Positive poling

Negative poling

MAPbIxCl3-x

Cur

rent

den

sity

(mA/

cm2 )

Voltage (V) -0.4 -0.2 0.0 0.2 0.4 0.6

-15-10-505

101520

Positive poling

Negative poling

HC(NH2)2PbI3

Cur

rent

den

sity

(mA/

cm2 )

Voltage (V)

-0.4 -0.2 0.0 0.2 0.4

-6

-3

0

3

6

9

MAPbBr3

Positive poling

Negative poling

Cur

rent

den

sity

(mA/

cm2 )

Voltage (V)

a

c

b

9

In order to confirm the ion drift induced photovoltaic switching mechanism, we examined other

three organolead trihalide perovksite materials, CH3NH3PbI3-xClx, HC(NH2)2PbI3 and

CH3NH3PbBr3 (Fig. S6). It is found all the devices with these materials as active layers showed

field switchable photovoltaic behavior.

Figure S7. Switchable photovoltaic effect of the ITO/PEDOT:PSS/Perovskite (300 nm)/Metal

vertical structure devices with different metal contacts of Pt, Ni and Ga. The devices were

scanned between ±2.5 V at a scanning rate of 0.14 V/s.

In order to examine whether gold is required for the switchable OTP devices, we tested other

metals like aluminum (Al), silver (Ag), platinum (Pt), gallium (Ga) and nickel (Ni) using the

-1.0 -0.5 0.0 0.5 1.0-20.0-15.0-10.0-5.00.05.0

10.015.020.0

Negative poling

Pt cathode

Positive poling

Cur

rent

den

sity

(mA

/cm

2 )

Voltage (V)-1.0 -0.5 0.0 0.5 1.0

-6

-4

-2

0

2

4

6

Negative poling

Positive PolingC

urre

nt d

ensi

ty (m

A/cm

2 )

Voltage (V)

Ni cathode

-0.4 -0.2 0.0 0.2 0.4 0.6-8.0-6.0-4.0-2.00.02.04.06.0

Negative poling

Ga cathode

Positive poling

Cur

rent

den

sity

(mA

/cm

2 )

Voltage (V)

a b

c





10

vertical device structure. Metal electrodes including Al, Ag, Pt, were deposited by thermal

evaporation or sputtering, metal electrode of Ga was formed by directly drop the Ga liquid on

perovskite films, and metal electrode of Ni was formed using Ni conductive tapes. None of the

devices were optimized to have high performance. The devices with inert metal electrodes like Pt

and Ni, and low work function metal of Ga also show switchable photovoltaic effect as shown in

Fig. S7. It was found that the thermally-evaporated Al and Ag reacted with the perovskite

because the deposited electrodes were black without metallic color, and the device performance

did not make any sense. The difference in short circuit current density can be explained by the

different active materials, electrode materials, and contacts between the electrodes and the

perovskite layers, because of the different electrode materials used and different fabrication

methods to form these electrodes.

-1.0 -0.5 0.0 0.5 1.0

-0.10

-0.05

0.00

0.05

0.10

Positive polingNegative poling

J SC (m

A/c

m2 )

VOC (V)

0.10 0.05 0.00 -0.05 -0.100

2

4

6 Positive poling

Cou

nt

Negative poling

JSC (mA/cm2)

-1.0 -0.5 0.0 0.5 1.00

2

4

6

8

10 Negative poling

C

ount

Positive poling

VOC (V)

Lateral structure devicesa

b

c

11

Figure S8. Photovoltaic performance statistics of the lateral structure devices. The lateral

structure devices were poled under 1.2 V/µm for 100 s, and photocurrent were measured under a

quarter sun illumination with a sweep rate of 0.05 V/s. a, distribution of the photovoltaic

performance of lateral structure devices in the JSC-VOC coordinate. b, VOC distribution of the

poled lateral structure devices; c, JSC distribution of the poled lateral structure devices.

Figure S9. J-V characteristics of the Au/perovskite (300 nm)/Au lateral structure devices with

different electrode spacing. The devices were poled under 1.2 V/µm for 100 s, and photocurrent

were measured under a quarter sun illumination with a sweep rate of 0.05 V/s.

Fig. S9 shows the normalized photocurrent curves with respect to the electrode spacing in

the Au/perovskite/Au lateral structure devices. In contrast to ferroelectric photovoltaic devices

10-410-310-210-1100

d=8 m

10-2

10-1

100

d=50 m

Nor

mal

ized

J(a

.u.)

-1.0 -0.5 0.0 0.5 1.0 1.5 2.010-2

10-1

100

d=100 m

Voltage (V)





12

whose VOC is proportional to the electrode spacing, the VOC of single lateral structure device

keeps almost constant at around 0.5 V regardless the electrode spacing variation from 8 µm to

100 µm. This result can exclude the contribution of potential ferroelectric property of the

perovskite, if it has, to the switchable photovoltaic effect observed.

-2 -1 0 1 2-40

-30

-20

-10

0

10

20

30

40

Remanent Polarization

Scanning rate: 0.08V/s at room temperature

Pol

ariz

atio

n (

C/c

m2 )

Voltage (V)-2 -1 0 1 2

-40

-30

-20

-10

0

10

20

30

40


Scanning rate: 0.08V/s at 77K

Pol

ariz

atio

n (

C/c

m2 )

Voltage (V)

a b

c d

e f

13

Figure S10. Ferroelectric polarization loops measured at room temperature (a) and at 77 K (b)

scanned at the same frequency of photovoltaic switch process. c, Piezoresponse force

microscopy (PFM) topology (c), amplitude (e) and phase (f) images of the perovskite (300 nm). d,

Representative PFM hysteresis loops (phase and amplitude) signal for any location on the film

surface.

Theoretical calculation predicted ferroelectric property of MAPbI3 with spontaneous

polarization of 38 µC/cm2 (1). We measured the ferroelectric hysteresis using the Precision

Premier Ⅱ from the Radiant technologies, Inc.. However we did not find any ferroelectric

polarization within the measurement range of the equipment from these devices both at room

temperature and at 77 K and using the same frequency of photovoltaic switch process. This

results further exclude the contribution of potential ferroelectric property of the perovskite, if it

has, to the switchable photovoltaic effect observed.





12

whose VOC is proportional to the electrode spacing, the VOC of single lateral structure device

keeps almost constant at around 0.5 V regardless the electrode spacing variation from 8 µm to

100 µm. This result can exclude the contribution of potential ferroelectric property of the

perovskite, if it has, to the switchable photovoltaic effect observed.

-2 -1 0 1 2-40

-30

-20

-10

0

10

20

30

40


Scanning rate: 0.08V/s at room temperature

Pol

ariz

atio

n (

C/c

m2 )

Voltage (V)-2 -1 0 1 2

-40

-30

-20

-10

0

10

20

30

40


Scanning rate: 0.08V/s at 77K

Pol

ariz

atio

n (

C/c

m2 )

Voltage (V)

a b

c d

e f

13

Figure S10. Ferroelectric polarization loops measured at room temperature (a) and at 77 K (b)

scanned at the same frequency of photovoltaic switch process. c, Piezoresponse force

microscopy (PFM) topology (c), amplitude (e) and phase (f) images of the perovskite (300 nm). d,

Representative PFM hysteresis loops (phase and amplitude) signal for any location on the film

surface.

Theoretical calculation predicted ferroelectric property of MAPbI3 with spontaneous

polarization of 38 µC/cm2 (1). We measured the ferroelectric hysteresis using the Precision

Premier Ⅱ from the Radiant technologies, Inc.. However we did not find any ferroelectric

polarization within the measurement range of the equipment from these devices both at room

temperature and at 77 K and using the same frequency of photovoltaic switch process. This

results further exclude the contribution of potential ferroelectric property of the perovskite, if it

has, to the switchable photovoltaic effect observed.





14

Figure S11. JSC output of the ITO/PEDOT:PSS/Perovskite (300 nm)/Au vertical structure

devices after negative and positive poling with time. The JSC were normalized by the value

measured at the starting point. The devices were poled at 6 V/µm for 20 s.

Fig. S11 shows the normalized JSC output measured overtime. It is obvious that, after

positive or negative poling, the device can output persistent photocurrent under light, which

excluded the contribution of charge traps to the switchable photovoltaic effect.

0 100 200 300 400-1.0-0.8-0.6-0.4-0.20.00.20.40.60.81.0

Negive poling Positive poling

Nor

mal

ized

JS

C (a

.u.)

Time (s)

15

Figure S12. AFM topography image (a), surface potential image (c) and adhesion image (d) of

the perovskite film after positive poling. AFM topography image of another film after negative

poling (b).

The Au electrode in topography image shown in Fig. S12 is not clear because the thickness of

the Au electrode is only about 50 nm, much smaller than the roughness (~150 nm) of the

perovskite thin films formed on glass. Nevertheless, we observed a clear difference of Au region

and perovskite region as well as the separation line between these two regions by examining the

adhesion mapping recorded during AFM scanning. The adhesion mapping of the exact same area

of Fig. 3e is shown in Fig. S12d. Adhesion is defined as the minimum tension (“pull-off”) forces

134.6 nm

-111.6 nm

102.1 nm

-95.4 nm

+ polingperovskite

Au

- polingperovskite

Au

a b

c d+ polingperovskite

+ polingperovskite





16

required for retracting the AFM tip from the sample surface. Many different types of interaction

forces, mainly van der Waals and/or electrostatic force, attribute to adhesion. Because the

interaction between tips with different materials have different adhesion, which constitutes the

contrast, this technology has been applied to a wide variety of materials to investigate the surface

heterogeneity or material distributions. As shown in Fig. 3e and Fig. S12d, the adhesion mapping

agrees well with the KPFM mapping.

Figure S13. A SEM image of a Au/perovskite/Au lateral structure device after poling

It shows the morphology change of perovskite after poling near the anode area. Compared

to the area far away from the anode, the area close to the Au electrode showed a lot of pin-holes

formed.

17

Figure S14. Dynamic poling process of the ITO/PEDOT:PSS/Perovskite (300 nm)/Au vertical

structure devices at (a) varied electrical field, (b-c) temperature and (d-f) with different film

morphology. The thickness of the films in d-f is 1,015 nm. (g) JSC versus poling time of the

devices with different film annealing processes and measurement temperatures. The devices were

measured under 0.1 sun when measured at 60 °C. The error bar showed the device performance

0 3 6 9 12 15-25-20-15-10-505

10152025

Temperature of measurement:

Film treatment:

RT

Thermal annealing Solvent annealing

J SC (m

A/cm

2 )

J SC (m

A/cm

2 )

Accumulated poling time (s)

-2

-1

0

1

2 60 oC

Thermal annealing

-20

-10

0

10

20 -1.5V pulseThickness 300 nm at RT

0 50 100 150 200-20

-10

0

10

20 -4.0 V pulse

Time (S)

-20

-10

0

10

20 -2.5V pulse

Curr

ent d

ensit

y (m

A/cm

2 )

-2

-1

0

1

2-2.5 V pulse At RT Thickness: 300 nm

0 50 100 150 200-2-1012 At 60oC

Time (s)

Curr

ent d

ensit

y (m

A/cm

2 )

a b

0 50 100 150 200-20-15-10

-505 Thermal annealing

Time (s)

-20-15-10

-505

-2.5 V pulseSolvent annealing

d e

1µm 1µm

f

Curr

ent d

ensit

y (m

A/cm

2 )

c

Curr

ent d

ensit

y (m

A/cm

2 )

-0.4 -0.2 0.0 0.2 0.4

-0.5

0.0

0.5

1.0

1.5

Voltage (V)

Positive poling

275 K

Negative poling

-0.4 -0.2 0.0 0.2 0.4

-0.5

0.0

0.5

Positive poling

250 K

Voltage (V)

Negative poling

g





18

variation based on the statistics of five devices of each category. And the scanning rate in Fig.

S14c was 0.14 V/s.

The drift of ions is expected to depend on temperature, electric field and the film

morphology. We studied the influence of these factors on the poling process by applying a train

of short voltage pulse (0.95 S) on the device and measured the device at JSC after each pulse to

avoid additional poling during the measurement. As shown in Fig. S14a-c, a larger electric field

or a higher poling temperature results in faster switching of the device. The switching of

photovoltaic was frozen under low temperature below 0 °C, where the photocurrent direction

cannot be switched by the same bias of ±2.5 V. It should be noted the data shown in Fig. 14a

were measured under 1 sun illumination, and the photocurrent in Fig. S14b were measured under

around 0.1 sun illumination due to the probe station setup limitation. Photocurrents in Fig. S14c

were measured with incident light penetrating the thin opaque Au electrodes, therefore the short

circuit current densities were much smaller than other cases.

Our recently developed solvent-annealing process resulted in larger grain size in the

perovskite films than the thermal-annealing, as shown in the cross-section scanning electron

microscopy images (Fig. S14d-e). We also tested the dynamic poling process of the devices with

perovskite films fabricated by solvent-annealing and thermal-annealing. The perovksite film with

larger grain size had fewer grain boundaries and thus less ion vacancies, which also resulted in

smaller ion drift velocity. As shown in Fig. S14e, the device with the solvent-annealed

perovskite films took much longer time to be switched than the thermal-annealed devices.



supplementary information · supplementary information. doi: 10.1038/nmat4150. nature materials | ...

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