1

Supporting for:

Interfacial stabilization for inverted perovskite solar cells with long-term

stability

Wei Chen1,2,† Bing Han1† Qin Hu,3,7†, Meng Gu,1 Yudong Zhu,1 Wenqiang Yang,4

Yecheng Zhou,5 Deying Luo,4 Fang-Zhou Liu,2 Rui Cheng,6 Rui Zhu,4 Shien Ping

Feng,6 Aleksandra B. Djurišić,2* Thomas P. Russell3,7* and Zhubing He1*

1Department of Materials Science and Engineering, Shenzhen Key Laboratory of Full

Spectral Solar Electricity Generation (FSSEG), Southern University of Science and

Technology, No. 1088, Xueyuan Rd., Shenzhen, 518055, Guangdong, P.R. China.

2Department of Physics, The University of Hong Kong, Pokfulam, Hong Kong SAR.

3Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley,

California 94720, USA.

4State Key Laboratory for Artificial Microstructure and Mesoscopic Physics,

Department of Physics, Peking University, Beijing 100871, China.

5Department of Physics, Southern University of Science and Technology, No. 1088,

Xueyuan Rd., Shenzhen, 518055, Guangdong, P.R. China.

6Department of Mechanical Engineering, The University of Hong Kong, Pokfulam,

Hong Kong SAR.

7Department of Polymer Science and Engineering, University of Massachusetts,

Amherst, Massachusetts 01003, United States.

†These authors contributed to this work equally.

2

Methods

Materials: N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO),

chlorobenzene (CB), Cesium iodide (CsI) were purchased from Sigma-Aldrich. Lead

(II) iodide (PbI2) and lead (II) bromide (PbBr2) were purchased from TCI.

Methylammonium bromide (MABr), formamidinium Iodide (FAI) and

phenethylammonium Iodide (PEAI) were purchased from GreatCell Solar Ltd.

Cl6SubPc and C60 were obtained from Daeyeon Chemicals Co.,Ltd. All materials

above were used as received.

Device fabrication. Perovskite solar cells (PVSCs) with p-i-n structure were

fabricated following a configuration of ITO/HTL/perovskite/ETLs/BCP/electrodes.

ITO glass was cleaned by sequentially washing with detergent, deionized water,

Acetone, and isopropanol. The substrates were dried with N2 and cleaned by UV

ozone for 15 min. Cu:NiOx HTLs were spin coated on the clean ITO substrates

according to our previous reports.1-3 The CsFAMA mixed perovskite layers were

fabricated according to our previously reported one-step antisolvent method.3 For

PEAI treatments, 100 µl PEAI solutions (2mg/ml in IPA) were quickly dropped on

CsFAMA mixed perovskite and spin coated with 5000 rpm for 45 s and annealed at

110 oC for 30 min. The substrates were then transferred into high vacuum thermal

evaporator where the ETLs Cl6SubPc (8 nm) and C60 (20 nm), BCP (8 nm) and metal

electrode (Ag (120 nm) or Cu (120 nm) or Au (80 nm)) were subsequently

evaporated. The active area was defined with a shadow mask.

Device and film characterization. J-V measurements were carried out using a

Keithley 2400 source meter in ambient environment at ~23 ºC and ~45% RH. The

devices were measured both in reverse scan (1.2 V→-0.2 V, step 0.01 V) and forward

scan (-0.2 V→1.2 V, step 0.01 V) with 10 ms delay time. Illumination was provided

by an Oriel Sol3A solar simulator with AM1.5G spectrum and light intensity of 100

mW/cm2, which was calibrated by a standard KG-5 Si diode. During I-V

measurement, optical aperture mask (8.939 mm2) was used to verify the accurate the

cell area. EQE measurements for devices were conducted with an Enli-Tech (Taiwan)

EQE measurement system. AFM-based experiments were measured in ambient

condition (25 ºC and 38% RH) with Atomic Force Microscope (MFP-3D-BIO,

Asylum Research, USA). Top-view morphology was analyzed by TESCAN MIRA3.

3

A FEI Helios Nanolab 600i dual beam focus ion beam/field emission gun-scanning

electron microscope (FIB/FEGSEM) was used to prepare cross-section for STEM

imaging and analysis. FEI Talos transmission electron microscope (TEM) with Super-

X EDX was employed to acquire the STEM-EDX data with STEM-HAADF (high-

angle annular dark field) mode. STEM-EELS was carried out on a double Cs-

corrected TEM (Titan Themis 60-300kV) performed by a Gatan cooling holder at the

liquid nitrogen temperature. For HR-TEM image, the prepared FIB lamina was then

immediately dropped in liquid nitrogen and transferred by a Cryo-transfer loader into

cryogenic chamber of Titan Krios cryo-TEM (Thermo Fisher Scientific Ltd.). The

cryo-TEM images were acquired using a low electron dose detector (Falcon, Thermo

Fisher Scientific Ltd.). The dose rate for each Cryo-TEM image is controlled to below

~50 e Å-2 S-1 for high resolution images and 1.5 e Å-2 S-1 for the low magnification

images, correspondingly. To decrease the dose rate, continuous 79 frames were

acquired in 2s and were integrated into one image with drift-correction aligned. The

operation voltage of electron beam is 300 kV. Depth profiling data were obtained

with ToF-SIMS 5 system from ION-TOF. The X-ray diffraction patterns were

obtained using a BRUKER ECO D8 series. Time resolved PL spectra were measured

using a Spectrofluorometer (FS5, Edinburgh instruments) and 405 nm pulsed laser

was used as excitation source for the measurement. UPS and XPS measurements were

performed on an ESCALAB 250Xi, Thermo Fisher (by using Al Kα x-ray source)

under high vacuum (10−9 mbar). The XPS spectra were calibrated by the binding

energy of C 1s. Mott–Schottky and density of states characteristics were analyzed

with a Zahner IM6e electrochemical station (Zahner, Germany) in ambient

environment of 25 ºC and 38% RH.

Grazing-incidence Wide-Angle X-ray Scattering (GIWAXS): GIWAXS

experiments were performed at beamline 7.3.3 of the Advanced Light Source (ALS),

Lawrence Berkeley National Laboratory (LBNL). The X-ray energy was 10 keV, and

the two-dimensional (2D) scattering patterns were acquired with a Dectris Pilatus 2M

CCD detector (172 µm x 172 µm pixel size). Grazing incidence angles of 0.5º was

collected to explore the crystal structure. All the perovskite films were deposited on

Si/Cu:NiOx substrates, while the Cl6SubPc and C60 films were deposited on Si

substrates. All the samples were imaged at ambient temperature in an enclosed

Helium box to ensure minimize background scattering. Data analysis was performed

4

using IGOR Pro software with the Nika package.

Device stability. For the maximum power point (MPP) tracking test, the encapsulated

device was fixed at the Vmpp and the current density variation under ambient

environment (~23.5 oC, 34% RH) was recorded without controlling the device

temperature. For thermal stability evaluation, the devices were stored in an inert

environment (O2 < 0.1ppm, H2O < 0.1ppm) at room temperature and/or 80 oC. The

devices were kept under dark except during the I-V measurement, and the I-V curves

were recorded in certain time intervals. For damp heat tests, the devices were stored at

environmental chamber with fixed temperature and humidity (85 oC and 85% RH)

except during the I-V measurement. For outdoor tests, the devices were mounted on

sample holder at 22º angle with the front side oriented towards the equator, located on

the rooftop without any blocking or shading of the sunshine. The devices for damp

heat, outdoor and MPPT in ambient environment under illumination tests were

carefully encapsulated with desiccant coverage in the cell area and epoxy edge sealing

following our previous encapsulation recipe.4

Theoretical calculations: DFT calculations: In order to investigate how the

molecules interact with perovksite layer and improve its stability, molecular dynamics

simulations were performed by Viena Ab initio Simulation Package 5. 4 (VASP),

which has been implemented with projector augmented wave (PAW) method. The

exchange-correlation of generalized gradient approximation (GGA) was described by

the Perdew–Burke–Ernzerhof (PBE) functional revised for solid, which gives lattice

constant close to experiments.5 The final adsoprtion configurations were relaxed from

structures obtained from an ab initio molecular dynamics (NVT ensemble , with

point) with a time step of 1 fs at 500 K for 3 ps. An energy cutoff of 450 eV was

employed. At least two possible adsorption configurations were achieved. In both

cases, two Cl ions of the molecules are bonded with Pb ions in perovskite, indicating

strong interaction between the perovskite and Cl6SubPc. The binding energies are

calculated to be -1.24 eV for the configurations. Compared to the binding energy (-

0.11 eV) of C60, the bond between Pb ions and Cl6SubPc is much stronger. For the

calculation of the binding energy between the 2D PEA+ cation (PEA-PEA), and the

PEA+ with Cl6SubPc molecule (PEA-Cl6SubPc-PEA), structure optimization and

5

energy calculations were performed by VASP 5.4.4, 6,7 which is implemented with

the projector-augmented wave potentials. PBE functional was used to describe the

exchange correlation. A cut off energy of Plane-wave basis sets is set as 550 eV. Due

to the big size of molecules, the used surface is very large (19.08×19.14 Å2) hence

only Γ-point was used to relax the structure and a Γ-point centered 3×3×1 k-mesh was

used for static energy calculations.

6

Supplementary Figure 1. I-V characteristics of the devices with and without 3D/2D

perovskite interfacial passivation and pure Cl6SubPc ETL.

Supplementary Figure 2. Statistics of device performance for the devices with

3D/2D perovskites and Cl6SubPc/C60 ETLs having different Cl6SubPc thickness.

7

Supplementary Table 1. Performance summaries of the optimal inverted PSCs with

different ETLs.

Devices Scan

direction Voc (V)

Jsc

(mA/cm2) FF (%)

PCE

(%)

3D PVK/C60 reverse 1.1 22.73 0.81 20.25

forward 1.09 22.75 0.8144 20.2

3D PVK/Cl6SubPc reverse 1.09 22.16 0.809 19.54

forward 1.08 22.20 0.806 19.32

3D/2D PVK/C60 reverse 1.130 22.94 0.804 20.82

forward 1.124 22.95 0.807 20.76

3D/2D PVK/Cl6SubPc reverse 1.12 22.82 0.802 20.5

forward 1.12 22.83 0.802 20.5

3D/2D PVK/Cl6SubPc/C60 reverse 1.16 23.31 0.812 22.0

forward 1.16 23.29 0.811 21.96

Supplementary Table 2. Performance summaries of the 3D/2D perovsikte PSCs with

different ETLs.

devices Averaged

Voc

(V) Averaged Jsc

(mA/cm2) Averaged FF

(%) Averaged PCE

(%)

3D/2D PVK/C60 1.105 22.762 77.49 19.49

3D/2D PVK/Cl6SubPc/C60 1.134 23.1915 79.37 20.86

8

Supplementary Table 3. Comparison the state-of-the-art performances of p-i-n

planar PSCs reported in the literature with present work.

HTLs ETLs Device

areaa

(mm2)

Voc (V)

Jsc

(mA/cm2) FF

(%) PCEb

(%) Certificationc

Light

Stabilityd Ref.

PTAA C60 6 1.15 23.2 80.4 21.6 N/A N/A 8

PTAA C60 8 1.14 23.7 78 21.0 20.59 26 h 9

PTAA PCBM/

C60 9 1.19 22.62 80 21.5 20.9 N/A 10

PTAA C60 8 1.18 22.5 81.7 21.7 N/A 500h 11

PTAA C60 / 1.21 22.49 78.5 21.4 N/A N/A 12

PTAA C60 / 1.15 23.4 80 21.5 N/A 500h 13

PTAA C60 8 1.16 22.63 80.4 21.1 N/A 1200h 14

PTAA C60 6.69 1.17 24.1 81.6 23.0 22.3 1000h 15

MPA-BTTI C60 12 1.12 23.23 81.4 21.17 N/A 500h 16

Cu:NiOx FA-

ZnO 10.8 1.14 22.83 81 21.11 N/A N/A 17

NiOx PCBM 12 1.12 23.18 80.2 20.86 N/A N/A 3

NiOx PCBM 12 1.15 22.89 79.5 20.96 N/A N/A 18

NiOx PCBM 9.19 1.08 23.8 81 19.8 N/A 1800h 19

NiOx PCBM 4 1.11

6 23.5 82 21.6 20.8 800h

20

Cu:NiOx Cl6Sub

Pc/C60 8.9 1.16 23.31 81.2 22 21.3

T90=2034 h

(T95=1200

h, ISOS-

O1)

This

work

a) The aperture area during IV measurements; b) Optimal values reported; c)

certification in an independent institute/organization; d) Operational stability with

MPPT method under continuous light illumination.

9

Supplementary Figure 3. Independent PCE certification for a p-i-n PSC in an

accredited PV Metrology Laboratory of NIM (National Institute of Metrology, China)

verified a PCE of 21.3% in reverse scan. The cell was tested in air without

encapsulation or protection during the test process ( 23.1oC, 63% RH).

10

Supplementary Figure 4. Device performances of the Cl6SubPc/C60 ETLs based

devices with different electrodes.

Supplementary Table 4. Performance of the optimal inverted PSCs with different

electrodes.

electrodes Scan

direction

Voc

(V)

Jsc

(mA/cm2)

FF

(%) PCE

(%)

Ag reverse 1.16 23.31 0.812 21.96

forward 1.16 23.29 0.811 21.91

Cu reverse 1.15 23.59 0.8015 21.75

forward 1.15 23.62 0.80 21.74

Au reverse 1.15 23.46 0.806 21.74

forward 1.14 23.43 0.812 21.69

11

Supplementary Figure 5. Top: SEM images of the 3D perovskite (left) and PEAI

treated 3D/2D perovskites (right). Bottom image shows the corresponding XRD

patterns.

12

Supplementary Figure 6. 2D GIWAXS profiles and analysis of perovskite samples.

2D scattering images of 3D CsFAMA perovskite (a), 3D/2D perovskite (b) and 3D/2D

perovskite/Cl6SubPc sample (c).

13

Supplementary Figure 7. 2D scattering images and the corresponding circle-

integrated line files of pure Cl6SubPc (a, b) and C60 (c, d).

Supplementary Figure 8. a) Detailed in plane (IP) and out of plane (OPP) files of

the circle-integrated line cuts of the corresponding samples; b) Detailed analysis of

the diffraction peaks in the GIWAXS. PVK and Sub denote perovskite and Cl6SubPc,

respectively.

14

Supplementary Figure 9. STEM images of the PSCs with Cl6SubPc/C60 ETL and

the corresponding EDX mapping of the marked area.

Supplementary Figure 10. STEM images of the PSCs with C60 ETL and the

corresponding EDX mapping of the marked area.

15

Supplementary Figure 11. Ab initio molecular dynamics (MD) optimization of the

Cl6SubPc on PbI2-terminated perovskite (001) with two different adsorption

configurations. The pure C60 control was also added for comparison.

16

Supplementary Figure 12. High resolution XPS profiles of Pb (a) and I (c) in the

3D/2D perovskite and Cl6SubPc coated 3D/2D perovskite films. (c) The High

resolution XPS profiles of Cl in the pure Cl6SubPc and Cl6SubPc coated 3D/2D

perovskite films.

17

Supplementary Table 5. Summaries of the decay life times for perovskite films with

different interlayers.

Sample direction A1

(%)

τ1

(ns)

A2

(%)

τ2

(ns)

τavg

(ns) a

2D/3D PVK Glass 100 741.2 - - 741.2

PVK 100 723.5 - - 723.5

2D/3D PVK

/C60

Glass 11.0 4.1 89.0 719.2 718.7

PVK 26.4 4.2 73.6 107.3 105.9

2D/3D PVK

/Cl6SubPc/C60

Glass 38.3 43.4 61.7 744.8 720.3

PVK 32 18.6 68 634.7 626.3

A 𝜏𝑎𝑣𝑔 refers to weighted average lifetime which is calculated as following: 𝜏𝑎𝑣𝑔 =𝐴1𝜏1

2+𝐴2𝜏22

𝐴1𝜏1+𝐴2𝜏2.

18

Supplementary Figure 13. Mott–Schottky characteristics for the C60 control and

Cl6SubPc/C60 ETLs based optimal PSCs.

19

Supplementary Figure 14. Light stabilities of the devices with C60 and

Cl6SubPc/C60 ETLs. The devices were carefully encapsulated and aged under

continuous 1 sun illumination in inert environments. The I-V measurement were

performed at different time intervals.

20

Supplementary Figure 15. Long term stabilities of the best device with C60 and

Cl6SubPc/C60 ETLs. The devices were stored in dark and inert environment, except

during the I-V measurement.

21

Supplementary Figure 16. Thermal stabilities of the devices with C60 and

Cl6SubPc/C60 ETLs. The devices were annealed at 80 oC in dark and inert

environment, except during the I-V measurement.

22

Supplementary Figure 17. Schematic layout design of device for the fully

encapsulation.

Supplementary Figure 18. Schematic diagram of each layer in the fully encapsulated

device.

23

Supplementary Figure 19. Accelerated stability tests of the 3D perovskite based

devices with pure C60 ETLs. The devices were tested in ambient environments

(~37% RH and ~ 45 oC) under 1 sun illumination. No attempt has been made to

control the temperature, and elevated temperature was a result of illumination.

Supplementary Figure 20. Light stability tests of the 3D perovskite with Cl6SubPc

and C60 ETLs with MPPT method under 1 sun illumination. The testing was

performed in ambient on encapsulated devices.

24

Supplementary Figure 21. Photos of the device with structure of ITO/NiOx/3D/2D

perovskite/C60/BCP/Ag before and after reverse bias (-1 V) for 4 hrs under light

illumination in ambient environment (65 RH%). Top panel shows the fresh device

(both Ag and glass side). The bottom panel shows the aged device. It is clear that the

Ag electrodes for the aged device have been severely damaged due to the reaction of

the halides with Ag. This reaction can be observed on the glass side, indicating the

diffusion of Ag+ into perovskite under reverse bias.

25

Supplementary Figure 22. Photos of the device with structure of ITO/NiOx/3D/2D

perovskite/Cl6SubPc(8 nm)/C60/BCP/Ag before and after reverse bias (-1V) for 8 hrs

under light illumination in ambient environment (65 RH%). Top panel shows the

fresh device (both Ag and glass side). The bottom panel shows the aged device.

Supplementary Figure 23. a) and b) Secondary-ion mass spectrometry (SIMS)

profiles of different positive (a) and negative (b) ions for the Cl6SubPc/C60 device

before and after aging.

26

Supplementary Figure 24. EELS mapping of the PVK/ETLs/electrodes interfaces

for the fresh 3D/2D PVK/C60 device. The aging of the device were performed by

continuous 1 sun illumination for 200 h in inert environment.

Supplementary Figure 25. High resolution XPS profiles of Ag and I in the C60

control device (a) and Cl6SubPc/C60 (b) device before and after aging.

27

Supplementary Figure 26. AFM topographic morphology and the corresponding

surface potential scans for the perovskite /C60 film as a function of illumination time.

Supplementary Figure 27. AFM topographic morphology and the corresponding

surface potential scans for the perovskite/Cl6SubPc/C60 film as a function of

illumination time.

28

Supplementary Figure 28. High resolution XPS profiles for I and N in the Cl6SubPc

films treated with iodide vapor.

Supplementary Figure 29. High resolution XPS profiles of N and B in PVK,

Cl6SubPc, and PVK/ Cl6SubPc.

Supplementary Figure 30. a) Molecular structure of the F16CuPc. J-V curve of the

best device based on 3D/2D perovskite and F16CuPc/C60 ETLs.

29

Supplementary Figure 31. Energy alignment of the different ETLs and the

perovskites. The data for F16CuPc was obtained from.21

30

Supplementary Figure 32. Light stabilities of the devices with C60 and

F16CuPc/C60 ETLs. The devices were encapsulated by sealing the edge area with

epoxy, and were illuminated under 1 Sun with mpp tracking.

Supplementary Figure 33. Photos of the device with structure of ITO/NiOx/3D/2D

perovskite/F16CuPc(8 nm)/C60/BCP/Ag before and after reverse bias (-1V) for 8 hrs

under light illumination in ambient environment (65 RH%). The thickness of the Top

panel shows the fresh device (both Ag and glass side). The bottom panel shows the

aged device.

31

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