Room-Temperature and Aqueous Solution-Processed Two

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Room Temperature and Aqueous Solution-Processed 2D TiS2 as Electron Transport Layer for Highly Efficient and Stable Planar n-i-p Perovskite Solar Cells Peng Huang, Ligang Yuan, Kai-cheng Zhang, Qiaoyun Chen, Yi Zhou, Bo Song, and Yongfang Li ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.8b03225 • Publication Date (Web): 10 Apr 2018 Downloaded from http://pubs.acs.org on April 10, 2018

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ACS Applied Materials & Interfaces

Room Temperature and Aqueous Solution-Processed 2D TiS2 as Electron Transport Layer for Highly Efficient and Stable Planar n-i-p Perovskite Solar Cells Peng Huang1, Ligang Yuan1, Kaicheng Zhang1, Qiaoyun Chen1, Yi Zhou, 1,* Bo Song, 1,* and Yongfang Li 1,2 1

Laboratory of Advanced Optoelectronic Materials, College of Chemistry Chemical Engineering and Materials Science, Soochow University, Suzhou, 215123, China

2

CAS Research/Education Center for Excellence in Molecular Sciences, CAS Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, China

Keywords: planar n-i-p perovskite solar cells, UVO-treated 2D TiS2, electron transport layer, room temperature and aqueous solution-processed

Abstract In this study, a room temperature and aqueous solution-processed 2D transition metal dichalcogenide TiS2 was applied as an electron transport layer (ETL) in planar n-i-p perovskite solar cells (Pero-SCs). Upon insertion of the 2D TiS2 ETL with UV-ozone (UVO) treatment, the power conversion efficiency (PCE) of the planar Pero-SCs was optimized to 18.79%. To the best of our knowledge, this value should be the highest efficiency to date among those PCEs of the n-i-p Pero-SCs with room temperature processed metal compound ETLs. More importantly, the n-i-p Pero-SCs with the UVO-treated 2D TiS2 as ETL also shows extremely high stability, where the average PCE remained over 95% of its initial value after 816 hours storage without encapsulation.

1. INTRODUCTION Organic-inorganic hybrid perovskite solar cells (Pero-SCs) show a high potential for application owing to its simple processing procedure, low-cost fabrication technique and high power conversion efficiency (PCE).1–8 Among the on-going research, the planar n-i-p 1 ACS Paragon Plus Environment

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configuration, in which the perovskite is sandwiched between the bottom transparent cathode with n-type electron transport layer (ETL) and top metal anode with p-type hole transport layer (HTL), attracted great attention recently.9–13 Under the attractive PCE, a shadow is still blocking the steps towards practical application of the devices, i.e., the poor stability caused by the decomposition of perovskite.14,15 Seeking of reliable interfacial layers that can promote the performance and at the same time more importantly improve the stability would be an important issue for the researchers in this area. Towards the twofold targets, high temperature (> 450 °C) processed ETLs (e.g. TiO2), 16–18 and low-temperature (~ 150 °C) processed ETLs (e.g. ZnO19,20 and SnO221,22) have been developed. Seeking for room temperature and aqueous solution-processed ETLs is not only for saving the cost by simplifying the processing procedure, but also bringing a chance to achieve highly stable photovoltaic devices. Considerable efforts have been made on exploring ETLs prepared at low (or room) temperature, but we are still not satisfactory on the presently developed materials / methods. For example, Li et al. achieved a PCE as high as 17.6% with application of an Al-doped ZnO layer prepared by radio frequency sputtering as ETL, however, this technique relies on expensive and complicated equipment that can be a limit for massive production.23 ZnO was presented as a good room temperature processed ETL and has drawn wide attention, however, up to date the moderate PCEs (< 16%) makes the ZnO ETL not encouraging.24,25 Moreover, TiO2 and ZnO could react with perovskite and exacerbate the decompostion of the perovskite deposited on it,26–28 and there is an urgent demand for the development of room temperature and aqueous solution-processed ETLs with good chemical stability for high performance Pero-SCs. Solution-processed two dimensional transition metal dichalcogenides (2D TMDs) prepared by exfoliation have shown a great potential as interfacial layers in planar Pero-SCs.29–32 In our previous work, we successfully applied room temperature and aqueous solution-processed 2D MoS2 and WS2 as hole transport layers in Pero-SCs.33 Along this research clue, we attempt to 2 ACS Paragon Plus Environment

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seek good 2D TMDs that can be employed as ETLs in n-i-p Pero-SCs. In the present study, room temperature and aqueous solution-processed 2D TiS2 was prepared by exfoliation, and used as an ETL due to its unique electronic and chemical properties.34–36 We found that the 2D TiS2 ETL with the treatment of UV-ozone (UVO) led to a great improvement of the device performance, and a PCE as high as 18.79% was achieved. To the best of our knowledge, this should be the highest PCE using room temperature processed metal compound ETLs. More importantly, the stability of the Pero-SCs became extremely high, and 95% of the average PCE was retained after 816 hours storage without encapsulation. We believe that the room temperature and aqueous solution-processed and UVO-treated 2D TiS2 possess a great potential as easily processible and environment friendly ETLs for highly efficient and stable Pero-SCs. 2. RESULTS AND DISCUSSION The 2D TiS2 was prepared by an ultrasonication-enhanced lithium interaction method.37 In brief, the TiS2 powder was reacted with n-butyllithium under vigorous ultrasonication, and thus exfoliated to nanosheets with a few atomic layers. X-ray diffraction (XRD) was employed to characterize the TiS2 before and after exfoliation. As shown in Figure 1a, the diffraction pattern of the bulk TiS2 accords with the standard peaks shown in the XRD pdf cards (JCPDS card No. 88-1967). After reaction, only (001) diffraction was observed, suggesting that the bulk TiS2 have been exfoliated into nanosheets.38,39 The formation of 2D TiS2 was also confirmed by transmission electron microscope (TEM) and atomic force microscopy (AFM), as shown in Figure 1(b-d). TEM image showed irregular nanosheets, and high-resolution image (inset) indicated the crystal lattice spacing of ~ 0.3 nm, which should be ascribed to (100), according well with that reported previously about 2D TiS2.37,40 The AFM image showed similar structures with TEM image, and the most probable thickness of the nanosheets determined by depth analysis was approximately 3.9 nm (corresponding to 3 layers ).41 It is worth to note that the 2D TiS2 is quite transparent for the visible light, which 3 ACS Paragon Plus Environment


can be evidenced by the UV-vis spectra (Figure S1 in supporting information) of ITO substrates before and after modification of approximately 10 nm of 2D TiS2.

0.3 nm

(001)

(b)

2 nm

(103)

2D TiS2 (003)

(011)

(001)

(a) Intensity (a.u.)

Bulk TiS2

200 nm 10

20

30

40

50

60

2θ (°)

(c)

(d)

8 nm 40 Count

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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20

0 nm 0 0

100 nm

2 4 6 8 Thickness (nm)

10

Figure 1. (a) XRD patterns of bulk TiS2, 2D TiS2 and JCPDS reference (black). (b) TEM image of 2D TiS2; inset, high resolution image. (c) AFM image of the 2D TiS2 and (d) The histogram of the thickness of 2D TiS2, analyzed from over 100 samples.

In the following, the work function (WF) of ITO with the 2D TiS2 film was determined by Kelvin probe force microscope (KPFM) using highly oriented pyrolytic graphite (HOPG) as reference, and the measurement method referred to the literature.42 As shown in Figure 2, the WF of pristine ITO was 4.75 eV, which is consistent with that reported in the literature.43 Upon modification with 2D TiS2, the WF increased to 4.79 eV. Such a WF does not match the conduction band (approximately 4.4 eV) of perovskite. Interestingly, a 15 min UVO treatment can effectively decrease the WF of the 2D TiS2-modified ITO to 4.64 eV. After UVO treatment, the energy level difference between the ITO and conduction band of perovskite is < 0.2 eV, suggesting that a smoother electron transfer should happen between them.44

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4.4 WF (eV)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Conduction Band of Perovskite

4.64

4.6

4.75 4.8

4.79

Figure 2. WFs of ITO with modification of 2D TiS2 and UVO-treated 2D TiS2. After UVO treatment, surface oxidation could happen, especially to TiS2, which was investigated by X-ray photoelectron spectroscopy (XPS). As shown in Figure 3a. the binding energies located at 531.6 and 532.9 eV corresponds to physically adsorbed oxygen on the surface and the oxygen chemically bonded with Ti4+, respectively.45,46 After UVO treatment, the relative content of bonded oxygen increased from 12.6% to 16.5%. It showed that the 2D TiS2 could be partially oxidized, which might passivate the structural defects such as S vacancies induced by lithium interaction46,47 and change the WFs of 2D TiS2 as schematized in Figure 3b. This was also reflected by the change of binding energy of Ti. The peaks located at 458.3 and 464.1 eV are assigned to the binding energy of Ti4+ 2p3/2 and Ti4+ 2p5/2, respectively. After UVO treatment, the location of corresponding peaks shifted to 458.5 and 464.3 eV, respectively, demonstrating partial oxidation of the 2D TiS2 at the surface due to UVO treatment.39,48



(a) Intensity (Counts)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

•

O 1s

•

Ti 2p

2D TiS2

UVO-treated 2D TiS2 536

532

528 468

462

456

Binding Binding energy (eV) Binding energy (eV) energy (eV)

(b)

UVO

2D TiS2

UVO treated-2D TiS2

(c)

Ti

S

(d)

Ti

S

Figure 3. (a) XPS spectra of 2D TiS2 and UVO-treated 2D TiS2. (b) schematic diagram of the oxidation surface of 2D TiS2 (yellow, green, red balls and dash circle stand for S, Ti, O atoms and S vacancy, respectively). SEM images of 2D TiS2 deposited ITO glass (c) before and (d) after UVO treatment and corresponding EDX maps for Ti and S element. (Scale bar, 1 µm)

As discussed above, the UVO treatment caused partial oxidation, and hence we were wondering if 2D TiS2 is still the dominating material in the modification layer. To unravel this question, energy dispersive X-ray (EDX) mappings were employed to evaluate the surface coverage. As shown in Figure 3c and 3d, the Ti and S elements of 2D TiS2 were still covering the whole vision after UVO treatment, indicating that 2D TiS2 was the majority. We fabricated planar n-i-p Pero-SCs using the 2D TiS2 as ETLs, and compared with devices without the ETL (control). The device configuration was ITO/ETL/perovskite/SpiroOMeTAD/Ag, as shown in Figure 4a &4b. The 2D TiS2 film was spin-coated on the ITO substrate, dried in a vacuum and treated with UVO for different durations. The optimized treatment time was 15 min, which was determined by the device performances (the corresponding data are presented in Figure S2, and detailed photovoltaic parameters are listed in Table S1). The perovskite film atop of ETL was prepared by two-step deposition method,49 6 ACS Paragon Plus Environment

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and the thickness was controlled to ~ 380 nm. A layer of Spiro-OMeTAD (~ 170 nm) was capped on perovskite films to facilitate the hole transportation (see Experimental Section for details). The optimal curves of the Pero-SCs based on different ETLs are shown in Figure 4c, and the photovoltaic parameters are summarized in Table 1. The highest PCE of the control device without the ETL under our experimental conditions was 13.42% with open circuit voltage (Voc) of 0.98 V, short circuit current density (Jsc) of 24.07 mA cm-2, and fill factor (FF) of 57.2%. Upon insertion of pristine 2D TiS2, the highest PCE dropped to 9.44% with Voc of 0.75 V, Jsc of 24.46 mA cm-2 and FF of 51.4%. Surprisingly, the PCE of the Pero-SC with the UVO-treated 2D TiS2 ETL skyrocketed to 18.79% with Voc of 1.00 V, Jsc of 24.75 mA cm-2 and FF of 75.2%. The Jsc of Pero-SCs with UVO-treated 2D TiS2 obtained from the J-V curves matched well with that integrated from the external quantum efficiency (EQE) curves as shown in Figure 4d, indicating the high reliability of the photovoltaic measurement. The PCE is comparable to that of the solar cells using high-temperature processed TiO2 or low-temperature processed SnO2 (or ZnO) as ETLs.20,50–52 The enhanced performance should be attributed to the decrease of the WFs and improvement of the electron transporting ability of the ETL. (c)

(b)

Ag

J (mA cm-2)

SpiroSpiro-OMeTAD

Perovksite

0.0

(d) 80

20

60

15

40

10

20

5

600

700

Wavelength (nm)

800

0

(e)

J ~ 21.54 mA cm

-2

25

0.4

0.6

0.8

1.0

8

(f)

20

15

PCE ~ 17.23%

15

10

10

5

5

0

0.2

V (V)

25 20

J (mA cm -2)

25

Intergrated (mA cm-2)

100

500

-20

1 μm

ITO

400

UVO-treated 2D TiS2

0

-10

2D TiS2

0 300

ITO 2D TiS2

10

0

50

100 150 200 250 300

0

Time (s)

PCE (%) Count

(a)

EQE (%)

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6 4 2 0 12

14

16 18 PCE (%)

20

Figure 4. (a) The schematic illustration of the device configuration and (b) cross-sectional SEM image of the corresponding device. (c) Typical J-V curves of the Pero-SCs with 7 ACS Paragon Plus Environment


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different ETLs under the illumination of AM1.5G, 100 mW cm-2. (d) EQE curve and integrated current density of the Pero-SC with UVO-treated 2D TiS2 as ETL. (e) Steady-state efficiency of the Pero-SC with UVO-treated 2D TiS2 as ETL. (f) histogram of the PCE of Pero-SCs with UVO-treated 2D TiS2, analyzed from 26 cells.

In addition, hysteresis of the J-V curves was observed as using forward and reverse scanning directions (Figure S3 and Table S2 in supporting information). Therefore, the steady-state photocurrents and efficiencies were measured to evaluate the operating performance of the Pero-SCs using the UVO-treated 2D TiS2 as ETL. The steady-state photocurrent at a constant bias of 0.80 V for 300 s under 100 mW cm-2 AM 1.5G illumination was 21.54 mA cm-2, corresponding to a stabilized output power of ~ 17.23% (Figure 4e), which is consistent with the intermediate value of the PCEs obtained from the reverse scans.

Table 1. Photovoltaic parameters of the Pero-SCs based on different ETLs under the illumination of AM1.5G, 100 mW cm-2. The average values and standard deviations were analysed from 26 cells. Voc (V)

Jsc (mA cm-2)

FF (%)

PCE (%)

ITO

0.98

24.07

57.2

13.42

2D TiS2

0.75

24.46

51.4

9.44

UVO-treated 2D TiS2

1.00

24.75

75.2

18.79

UVO-treated 2D TiS2 (statistics)

0.96 ± 0.04

24.68 ± 0.32

70.1 ± 3.3

16.72 ± 1.20

To assess the reproducibility, we analyzed 26 cells prepared from several batches. As shown in the histogram in Figure 4f, the PCE varied in a very narrow range. The deviations of the detailed parameters shown in Table 1 are also very small, indicating the device performance possesses quite good reproducibility. To show the novelty of this study, we compared our result with the reported PCEs of the planar n-i-p Pero-SCs with room temperature processed metal compound ETLs in Figure 5. It can be seen that only a few ETLs can result in PCEs higher than 17%, and the top three PCEs 8 ACS Paragon Plus Environment

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except for this study were achieved using ETLs prepared with sputtering method. Utilizing UVO-treated 2D TiS2 as ETL, we were able to obtain a PCE as high as 18.79%, which should be the highest efficiency among the Pero-SCs using room temperature processed metal compound ETLs. 19 18

PCE (%)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


17 16

★ 2D TiS2, This work Al-doping ZnO， ref. 23 TiO2， ref. 57 Nb2O5， ref. 56 TiOx， ref. 55 ZnO， ref. 25 ZnO， ref. 24

15 Zn2SnO4， ref. 54

Preparation of ETLs

14 13

Solution-processing Sputtering

W(Nb)Ox， ref. 53

Figure 5. Comparison of PCEs of the n-i-p Pero-SCs based on different ETL materials of W(Nb)Ox,53 Zn2SnO4,54 ZnO,24 ZnO,25 TiOx,55 Nb2O5,56 TiO2,57 Al-doped ZnO,23 with different preparation method.

To further study the effect of the UVO-treated 2D TiS2 ETL on performance of the devices, the photocurrent density -effective voltage (Jph - Veff) curves43,58 were recorded for the devices without and with the UVO-treated 2D TiS2 ETL. Figure 6a shows the Jph - Veff curves in double-logarithmic coordinates. Jph is determined by the equation Jph = JL - JD, in which JL and JD are the current densities under illumination and in the dark, respectively. The corresponding values of JD are shown in Figure S4 in supporting information. Veff is calculated from the equation Veff = Vo-V, where V is the applied voltage and Vo is the voltage at Jph = 0. As shown in Figure 6b, the Jphs of both devices possess a similar trend, which first increased linearly until 0.1 V and then reached to a saturated level at ~ 1 V. Moreover, at small Veffs the Pero-SC with the UVO-treated 2D TiS2 ETL demonstrates higher Jph than that without, which indicates a higher charge extraction efficiency, and consequently a higher FF.49,59,60 9 ACS Paragon Plus Environment


(a)

(b)

Rs

Rtr

Rrec

C1

C2

600

-Z '' (Ω)

Jph (mA cm-2)

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10

400

200

ITO UVO-treated 2D TiS2

0 0.1

1

0

200

400

600

800

1000

Z ' (Ω)

Veff (V)

Figure 6. (a) Jph-Veff curves of the Pero-SCs with and without the UVO-treated 2D TiS2 ETL. (b) Nyquist plots; inset: the equivalent circuit used to fit the impedance curves. (C, ideal capacitor).

The electrochemical impedance spectroscopy (EIS) was employed to study the charge transportation of the series of Pero-SCs. The measurement was carried out in the dark at the applied voltage near to the corresponding Voc, and the Nyqiust plots were presented in Figure 6b. The inset is the circuit employed to fit the plots, and the detailed parameters were summarized in Table 2. The hemi-cycle at the high and low frequencies are ascribed to the transport (Rtr) and recombination resistances (Rrec), respectively.61 It was found that Rtr dramatically decreased from 839.1 to 230.3 Ω when UVO-treated 2D TiS2 was introduced as ETL. While, Rrec increased from 45.0 to 268.8 Ω. The decreased Rtr and increased Rrec both suggest a facilitated charge transportation and a lower recombination rate of charge carriers in the Pero-SCs based on the UVO-treated 2D TiS2 ETL, thus resulting in an improved Jsc and FF.33,62,63 These results are in good agreement with the photovoltaic parameters obtained from the J-V curves.

Table 2. The parameters of equivalent circuit fitted from the Nyquist plots of the Pero-SCs with and without the UVO-treated 2D TiS2 ETL. Rs (Ω)

Rtr (Ω)

C1 (nF)

Rrec (Ω)

C2 (nF)

ITO

25.2

839.1

1.3

45.0

2.0

UVO-treated 2D TiS2

19.6

230.3

2.3

268.8

3.0


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In addition to PCE, stability is another key parameter for the practical applications of PeroSCs. Herein the stability of the Pero-SCs without encapsulation was investigated at atmosphere conditions with relative humidity (RH) of ~ 10%. Figure 7a shows the J-V curves of the devices taken at the first day and after 816 hours storage. The device maintained 95.8% of its initial PCE after 816 hours storage. In addition to the PCE, the detailed parameters, such as Voc, Jsc, and FF, also didn't change too much. To testify the effect of humidity on the stability, the unencapsulated devices were stored under ambient environment with 45-60% RH. As shown in Figure S5, after 100 h exposure, the Pero-SCs still retained over 80% of the initial PCEs. These results indicate that the application of UVO-treated 2D TiS2 ETL brought us an extremely high stability for the Pero-SCs.

-20

0.85

0.4

0.6

V (V)

0.8

1.0

0.80

Jsc

25 24

0

200

400

600

800

FF 21

23

Time (h)

72 20 69

19

66

PCE

63 60

18

PCE (%)

-15

0.2

26

0.95

22

(c) 75

27

1.00

0.90

-25 0.0

Voc

1.05

FF (%)

Fresh device After 816 h

Voc: ~ 1.01 V 1.02V -5 Jsc: ~ 24.5 mA cm-2 24.4 mA cm-2 70.5% ~ 73.9% -10 FF: 17.61% PCE: ~ 18.38%

Voc (V)

0

(b)

Jsc (mA cm-2)

(a) 5

J (mA cm-2)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


17 0

200

400

600

800

16

Time (h)

Figure 7. (a) J-V curves of the Pero-SCs with UVO-treated 2D TiS2 as ETL under the illumination of AM1.5G, 100 mW cm-2, taken from the very first day and after 816 hours storage at atmosphere conditions with RH of ~ 10%. (b) and (c) average photovoltaic parameters of the Pero-SCs versus the storage time.

3. CONCLUSION In conclusion, the room temperature aqueous solution-processed 2D TiS2 was prepared by exfoliation, and employed as ETLs in planar n-i-p Pero-SCs. The pristine 2D TiS2 ETL resulted in a decrease of PCE comparing with the devices without the ETL, while the UVOtreated 2D TiS2 ETL led to a surprising increase of PCE. Under the optimal conditions, a PCE as high as 18.79% was achieved, which to the best of our knowledge is the highest efficiency 11 ACS Paragon Plus Environment


among the planar n-i-p Pero-SCs ever reported using room-temperature processed metal compound ETLs. More importantly, the Pero-SCs with the UVO-treated 2D TiS2 ETL demonstrated an extremely high stability, and the average PCEs without encapsulation remained over 95% of initial efficiencies after being stored at atmosphere conditions with RH of ~ 10% for more than 800 hours. 4. EXPERIMENTAL SECTION Synthesis of 2D TiS2. 2D TiS2 was synthesized following the previous report.37 In brief, 0.2 g of bulk TiS2 (99%, Alfa Aesar) was first added into a two-necked flask and degassed for 3 times. After that, two-necked flask was sealed and protected with Ar. 7.4 mL of 2.4 mol L-1 butyllithium solution in hexane (Amethyst) was injected into two-necked flask. Lithium intercalation of TiS2 was performed in an ultrasonicator for 180 min. Before exfoliation, the flask was kept still for 30 min and the residual butyllithium in supernatant was removed. 10 mL of deaerated deionized water was injected into the flask. The aqueous suspension of TiS2 was sonicated for 30 min to complete the exfoliation. 10 mL of ethanol was introduced into the suspension and centrifuged at 9500 rpm for 5 min, the residue was added into 10 mL of ethanol and centrifuged at 9500 rpm for 5 min. The sediment was separated and dispersed in deionized water. After being centrifuged at 5000 rpm for 5 min, the supernatant was collected. Fabrication of Pero-SCs with UVO-treated 2D TiS2 as ETL. 2D TiS2 films were spin-coated on the ITO pretreated with UVO at 3000 rpm for 30 s. The ITO substrates with 2D TiS2 was treated by UVO for 15 min before drying in a vacuum oven at room temperature. The perovskite layer was fabricated by two-step deposition method.49,64 The 1.3 mol L-1 PbI2 was dissolved in mixed solution (DMF : DMSO = 9.5 : 0.5) and the mixture solution of formamidinium iodide (FAI): methylammonium bromide (MABr) : methylammonium chloride (MACl) (60 mg : 6 mg : 6 mg in) was dissolved in 1 mL isopropanol. The PbI2 was spun on ITO/UVO-treated 2D TiS2 at 4000 rpm for 20 s, then a drop of mixture solution containing FAI, MABr and MACl was dropped on the centre of spin-coated wet precursor 12 ACS Paragon Plus Environment

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film for 30 s. The as prepared samples were annealed at 150 °C for 15 min in ambient air condition (30 - 40 % humidity). The HTL was deposited on top of the perovskite film by 3500 rpm for 30 s using Spiro-OMeTAD solution, which consisted of 50.61 mg, 20.2 µL 4tertbutylpyridine, 12.25 µL bis(trifluoromethane) sulfonimide lithium salt (Li-TFSI) stock solution (520 mg Li-TFSI in 1 mL acetonitrile) and 0.7 mL chlorobenzene. Finally, Ag (100 nm) were sequentially deposited by thermal evaporation. Characterization. XRD data of TiS2 was collected on D2 PHASER. TEM images were obtained on a FEI Tecnai F20 with operating voltage of 200 kV. AFM images were captured on a MutiMode 8 microscope (Bruker, Santa Barbara, CA) with peak force quantitative nanomechanical mode in air. The transmittance of ITO with 2D TiS2 before and after UVO treatment was collected by Cary 5000 UV-Vis-NIR. The WFs of ITO with 2D TiS2 and UVOtreated 2D TiS2 was measured by KPFM in air. The chemical state of 2D TiS2 and UVOtreated 2D TiS2 was determined by XPS (Escalab 250Xi). EDX mapping images of ITO/2D TiS2 and ITO/UVO-treated 2D TiS2 were recorded on an S-8010 (Hitachi) with applied acceleration voltage of 15 kV. The J-V curves of Pero-SCs were recorded using a Keithley 2400 source meter placed in a glove box filled with nitrogen. The measurement was conducted under AM 1.5G solar illumination with an intensity of 100 mW cm-2 in reverse scan (1.2 V to 0 V) at a speed of 2 V s-1. A shadow mask was clung to the substrate to define an active area of 7.57 mm2. The EQE was measured by using a solar cell spectral response measurement system (Enli Technology Co., Ltd, QE-R3011) in air. EIS curves were measured on an IM6 electrochemical workstation (Zahner Zennium, Germany) in the dark with a bias near the corresponding Voc of individual cells.

ASSOCIATED CONTENT Supporting Information



The Supporting Information is available free of charge on the ACS Publications website at DOI: UV-vis transmittance spectra; J-V curves of devices with different UVO treatment time on 2D TiS2; J-V curves of device at both forward and reverse scans; J-V curves measured in the dark.

AUTHOR INFORMATION Corresponding Authors

*E-mail:[email protected]; [email protected].

ACKNOWLEDGEMENTS This work was supported by the National Natural Science Foundation of China (51673139, 91633301), Priority Academic Program Development of Jiangsu Higher Education Institutions, State and Local Joint Engineering Laboratory for Novel Functional Polymeric Materials.

REFERENCES (1)

(2)

(3)

(4)

(5)

(6)

Arora, N.; Dar, M. I.; Hinderhofer, A.; Pellet, N.; Schreiber, F.; Zakeeruddin, S. M.; Grätzel, M. Perovskite Solar Cells with CuSCN Hole Extraction Layers Yield Stabilized Efficiencies Greater Than 20%. Science. 2017, 358, 768–771. Wu, Y.; Xie, F.; Chen, H.; Yang, X.; Su, H.; Cai, M.; Zhou, Z.; Noda, T.; Han, L. Thermally Stable MAPbI3 Perovskite Solar Cells with Efficiency of 19.19% and Area over 1 cm2 Achieved by Additive Engineering. Adv. Mater. 2017, 29, 1701073. Zuo, L.; Guo, H.; DeQuilettes, D. W.; Jariwala, S.; De Marco, N.; Dong, S.; DeBlock, R.; Ginger, D. S.; Dunn, B.; Wang, M.; Polymer-Modified Halide Perovskite Films for Efficient and Stable Planar Heterojunction Solar Cells. Sci. Adv. 2017, 3, e1700106. Aitola, K.; Domanski, K.; Correa-Baena, J.-P.; Sveinbjörnsson, K.; Saliba, M.; Abate, A.; Grätzel, M.; Kauppinen, E.; Johansson, E. M. J.; Tress, W.; High TemperatureStable Perovskite Solar Cell Based on Low-Cost Carbon Nanotube Hole Contact. Adv. Mater. 2017, 29, 1606398. Zhang, X.; Ren, X.; Liu, B.; Munir, R.; Zhu, X.; Yang, D.; Li, J.; Liu, Y.; Smilgies, D.M.; Li, R.; Stable High Efficiency Two-Dimensional Perovskite Solar Cells via Cesium Doping. Energy Environ. Sci. 2017, 10, 2095–2102. Alcocer, M. J. P.; Leijtens, T.; Herz, L. M.; Petrozza, A.; Snaith, H. J.; Stranks, S. D.; Eperon, G. E.; Grancini, G.; Menelaou, C.; Alcocer, M. J. P.; Electron-Hole Diffusion Lengths Exceeding 1 Micrometer in an Organometal Trihalide Perovskite Absorber. Science. 2013, 342, 341–344.


Page 14 of 19

Page 15 of 19 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(7)

(8)

(9)

(10)

(11) (12)

(13)

(14)

(15) (16)

(17) (18)

(19)

(20)

(21)

(22)

Kojima, A.; Teshima, K.; Shirai, Y.; Miyasaka, T. Organometal Halide Perovskites as Visible-Light Sensitizers for Photovoltaic Cells. J. Am. Chem. Soc. 2009, 131, 6050– 6051. Liu, X.; Huang, P.; Dong, Q.; Wang, Z.; Zhang, K.; Yu, H.; Lei, M.; Zhou, Y.; Song, B.; Li, Y. Enhancement of the Efficiency and Stability of Planar p-i-n Perovskite Solar Cells via Incorporation of an Amine-Modified Fullerene Derivative as a Cathode Buffer Layer. Sci. China Chem. 2017, 60, 136–143. Zhang, J.; Xu, L. J.; Huang, P.; Zhou, Y.; Zhu, Y. Y.; Yuan, N. Y.; Ding, J. N.; Zhang, Z. G.; Li, Y. F. A Simple and Dopant-Free Hole-Transporting Material Based on (2Ethylhexyl)-9H -Carbazole for Efficient Planar Perovskite Solar Cells. J. Mater. Chem. C 2017, 5, 12752–12757. Xu, L.; Huang, P.; Zhang, J.; Jia, X.; Ma, Z.; Sun, Y.; Zhou, Y.; Yuan, N.; Ding, J. N, N-Di-para-methylthiophenylamine-Substituted (2-Ethylhexyl)-9H-Carbazole: A Simple, Dopant-Free Hole-Transporting Material for Planar Perovskite Solar Cells. J. Phys. Chem. C 2017, 121, 21821–21826. Yang, Z.; Rajagopal, A.; Jen, A. K. Y. Ideal Bandgap Organic-Inorganic Hybrid Perovskite Solar Cells. Adv. Mater. 2017, 29, 1704418. Reddy, S. S.; Shin, S.; Aryal, U. K.; Nishikubo, R.; Saeki, A.; Song, M.; Jin, S.-H. Highly Efficient Air-Stable/Hysteresis-Free Flexible Inverted-Type Planar Perovskite and Organic Solar Cells Employing a Small Molecular Organic Hole Transporting Material. Nano Energy 2017, 41, 10–17. Paek, S.; Qin, P.; Lee, Y.; Cho, K. T.; Gao, P.; Grancini, G.; Oveisi, E.; Gratia, P.; Rakstys, K.; Al-Muhtaseb, S. A.; Dopant-Free Hole-Transporting Materials for Stable and Efficient Perovskite Solar Cells. Adv. Mater. 2017, 29, 1606555. Wang, Z.; Shi, Z.; Li, T.; Chen, Y.; Huang, W. Stability of Perovskite Solar Cells: A Prospective on the Substitution of the A Cation and X Anion. Angew. Chem. Int. Ed. 2017, 56, 1190–1212. Niu, G.; Guo, X.; Wang, L. Review of Recent Progress in Chemical Stability of Perovskite Solar Cells. J. Mater. Chem. A 2015, 3, 8970–8980. Yang, W. S.; Park, B. W.; Jung, E. H.; Jeon, N. J.; Kim, Y. C.; Lee, D. U.; Shin, S. S.; Seo, J.; Kim, E. K.; Noh, J. H.; Iodide Management in Formamidinium-Lead-Halidebased Perovskite Layers for Efficient Solar Cells. Science. 2017, 356, 1376–1379. Yang, G.; Tao, H.; Qin, P.; Ke, W.; Fang, G. Recent Progress in Electron Transport Layers for Efficient Perovskite Solar Cells. J. Mater. Chem. A 2016, 4, 3970–3990. Docampo, P.; Ball, J. M.; Darwich, M.; Eperon, G. E.; Snaith, H. J. Efficient Organometal Trihalide Perovskite Planar-Heterojunction Solar Cells on Flexible Polymer Substrates. Nat. Commun. 2013, 4, 2761. An, Q.; Fassl, P.; Hofstetter, Y. J.; Becker-Koch, D.; Bausch, A.; Hopkinson, P. E.; Vaynzof, Y. High Performance Planar Perovskite Solar Cells by ZnO Electron Transport Layer Engineering. Nano Energy 2017, 39, 400–408. Zhao, Y.; Zhang, K.; Wang, Z.; Huang, P.; Zhu, K.; Li, Z.; Li, D.; Yuan, L.; Zhou, Y.; Song, B. Comprehensive Study of Sol–Gel versus Hydrolysis–Condensation Methods To Prepare ZnO Films: Electron Transport Layers in Perovskite Solar Cells. ACS Appl. Mater. Interfaces 2017, 9, 26234–26241. Jiang, Q.; Zhang, L.; Wang, H.; Yang, X.; Meng, J.; Liu, H.; Yin, Z.; Wu, J.; Zhang, X.; You, J. Enhanced Electron Extraction Using SnO2 for High-Efficiency PlanarStructure HC(NH2)2PbI3-Based Perovskite Solar Cells. Nat. Energy 2016, 2, 16177– 16183. Ke, W.; Fang, G.; Liu, Q.; Xiong, L.; Qin, P.; Tao, H.; Wang, J.; Lei, H.; Li, B.; Wan, J.; Low-Temperature Solution-Processed Tin Oxide as an Alternative Electron 15 ACS Paragon Plus Environment


(23)

(24)

(25) (26)

(27)

(28)

(29)

(30)

(31)

(32)

(33)

(34)

(35)

(36)

(37)

(38)

Transporting Layer for Efficient Perovskite Solar Cells. J. Am. Chem. Soc. 2015, 137, 6730–6733. Tseng, Z. L.; Chiang, C. H.; Chang, S. H.; Wu, C. G. Surface Engineering of ZnO Electron Transporting Layer via Al Doping for High Efficiency Planar Perovskite Solar Cells. Nano Energy 2016, 28, 311–318. Liu, D. Y.; Kelly, T. L. Perovskite Solar Cells with a Planar Heterojunction Structure Prepared Using Room-Temperature Solution Processing Techniques. Nat. Photonics 2014, 8, 133–138. Tseng, Z.-L.; Chiang, C.-H.; Wu, C.-G. Surface Engineering of ZnO Thin Film for High Efficiency Planar Perovskite Solar Cells. Sci. Rep. 2015, 5, 13211. Ito, S.; Tanaka, S.; Manabe, K.; Nishino, H. Effects of Surface Blocking Layer of Sb2S3 on Nanocrystalline TiO2 for CH3NH3PbI3 Perovskite Solar Cells. J. Phys. Chem. C 2014, 118, 16995–17000. Zhang, J.; Pauporté, T. Effects of Oxide Contact Layer on the Preparation and Properties of CH3NH3PbI3 for Perovskite Solar Cell Application. J. Phys. Chem. C 2015, 119, 14919–14928. Kumar, S.; Dhar, A. Accelerated Thermal-Aging-Induced Degradation of Organometal Triiodide Perovskite on ZnO Nanostructures and its Effect on Hybrid Photovoltaic Devices. ACS Appl. Mater. Interfaces 2016, 8, 18309–18320. Dai, R.; Wang, Y.; Wang, J.; Deng, X. Metal-Organic-Compound-Modified MoS2 with Enhanced Solubility for High-Performance Perovskite Solar Cells. ChemSusChem 2017, 10, 2869–2874. Kim, Y. G.; Kwon, K. C.; Le, Q. Van; Hong, K.; Jang, H. W.; Kim, S. Y. Atomically Thin Two-Dimensional Materials as Hole Extraction Layers in Organolead Halide Perovskite Photovoltaic Cells. J. Power Sources 2016, 319, 1–8. Capasso, A.; Matteocci, F.; Najafi, L.; Prato, M.; Buha, J.; Cinà, L.; Pellegrini, V.; Carlo, A. Di; Bonaccorso, F. Few-Layer MoS2 Flakes as Active Buffer Layer for Stable Perovskite Solar Cells. Adv. Energy Mater. 2016, 6, 1600920. Dasgupta, U.; Chatterjee, S.; Pal, A. J. Thin-Film Formation of 2D MoS2 and its Application as a Hole-Transport Layer in Planar Perovskite Solar Cells. Sol. Energy Mater. Sol. Cells 2017, 172, 353–360. Huang, P.; Wang, Z.; Liu, Y.; Zhang, K.; Yuan, L.; Zhou, Y.; Song, B.; Li, Y. WaterSoluble 2D Transition Metal Dichalcogenides as the Hole-Transport Layer for Highly Efficient and Stable p–i–n Perovskite Solar Cells. ACS Appl. Mater. Interfaces 2017, 9, 25323–25331. Conroy, L. E.; Park, K. C. Electrical Properties of the Group IV Disulfides, Titanium Disulfide, Zirconium Disulfide, Hafnium Disulfide and Tin Disulfide. Inorg. Chem. 1968, 7, 459–463. Liu, Z.; Lau, S. P.; Yan, F. Functionalized Graphene and Other Two-Dimensional Materials for Photovoltaic Devices: Device Design and Processing. Chem. Soc. Rev. 2015, 44, 5638–5679. Singh, E.; Kim, K. S.; Yeom, G. Y.; Nalwa, H. S. Atomically Thin-Layered Molybdenum Disulfide (MoS2) for Bulk-Heterojunction Solar Cells. ACS Appl. Mater. Interfaces 2017, 9, 3223–3245. Yuwen, L.; Yu, H.; Yang, X.; Zhou, J.; Zhang, Q.; Zhang, Y.; Luo, Z.; Su, S.; Wang, L. Rapid Preparation of Single-Layer Transition Metal Dichalcogenide Nanosheets via Ultrasonication Enhanced Lithium Intercalation. Chem. Commun. 2016, 52, 529–532. Nguyen, T. P.; Choi, S.; Jeon, J.-M. M.; Kwon, K. C.; Jang, H. W.; Kim, S. Y. Transition Metal Disulfide Nanosheets Synthesized by Facile Sonication Method for the Hydrogen Evolution Reaction. J. Phys. Chem. C 2016, 120, 3929–3935. 16 ACS Paragon Plus Environment

Page 16 of 19

Page 17 of 19 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(39)

(40)

(41)

(42)

(43)

(44)

(45)

(46)

(47)

(48)

(49)

(50)

(51)

(52) (53)

(54)

Liu, Y.; Liang, C.; Wu, J.; Sharifi, T.; Xu, H.; Nakanishi, Y.; Yang, Y.; Woellne, C. F.; Aliyan, A.; Martí, A. A.; Atomic Layered Titanium Sulfide Quantum Dots as Electrocatalysts for Enhanced Hydrogen Evolution Reaction. Adv. Mater. Interfaces 2018, 5, 1700895. Lin, C.; Zhu, X.; Feng, J.; Wu, C.; Hu, S.; Peng, J.; Guo, Y.; Peng, L.; Zhao, J.; Huang, J.; Hydrogen-Incorporated TiS2 Ultrathin Nanosheets with Ultrahigh Conductivity for Stamp-Transferrable Electrodes. J. Am. Chem. Soc. 2013, 135, 5144–5151. Zeng, Z.; Yin, Z.; Huang, X.; Li, H.; He, Q.; Lu, G.; Boey, F.; Zhang, H. Single-Layer Semiconducting Nanosheets: High-Yield Preparation and Device Fabrication. Angew. Chemie Int. Ed. 2011, 50, 11093–11097. Xia, Y.; Song, B. KPFM and its Use to Characterize the CPD in Different Materials. In Atomic Force Microscopy: Applications in Nanomaterials; Wiley-VCH: Weinheim, Germany, 2017; pp 297–312. Li, Z.; Liu, Y.; Zhang, K.; Wang, Z.; Huang, P.; Li, D.; Zhou, Y.; Song, B. Chemical Modification of n-Type-Material Naphthalene Diimide on ITO for Efficient and Stable Inverted Polymer Solar Cells. Langmuir 2017, 33, 8679–8685. Cao, T.; Huang, P.; Zhang, K.; Sun, Z.; Zhu, K.; Yuan, L.; Chen, K.; Chen, N.; Li, Y. Interfacial Engineering via Inserting Functionalized Water-Soluble Fullerene Derivative Interlayers for Enhancing the Performance of Perovskite Solar Cells. J. Mater. Chem. A 2018, 6, 3435–3443. Xing, W.; Chen, Y.; Wang, X.; Lv, L.; Ouyang, X.; Ge, Z.; Huang, H. MoS2 Quantum Dots with a Tunable Work Function for High-Performance Organic Solar Cells. ACS Appl. Mater. Interfaces 2016, 8, 26916–26923. Yang, X.; Fu, W.; Liu, W.; Hong, J.; Cai, Y.; Jin, C.; Xu, M.; Wang, H.; Yang, D.; Chen, H. Engineering Crystalline Structures of Two-Dimensional MoS2 Sheets for High-Performance Organic Solar Cells. J. Mater. Chem. A 2014, 2, 7727–7733. Kim, C.; Nguyen, T. P.; Le, Q. Van; Jeon, J. M.; Jang, H. W.; Kim, S. Y. Performances of Liquid-Exfoliated Transition Metal Dichalcogenides as Hole Injection Layers in Organic Light-Emitting Diodes. Adv. Funct. Mater. 2015, 25, 4512–4519. Dupin, J. .; Gonbeau, D.; Martin-Litas, I.; Vinatier, P.; Levasseur, A. Amorphous Oxysulfide Thin Films MOySz (M=W, Mo, Ti) XPS Characterization: Structural and Electronic Pecularities. Appl. Surf. Sci. 2001, 173, 140–150. Huang, P.; Liu, Y.; Zhang, K.; Yuan, L.; Li, D.; Hou, G.; Dong, B.; Zhou, Y.; Song, B.; Li, Y. Catechol Derivatives as Dopants in PEDOT:PSS to Improve the Performance of p–i–n Perovskite Solar Cells. J. Mater. Chem. A 2017, 5, 24275–24281. Roose, B.; Johansen, C. M.; Dupraz, K.; Jaouen, T.; Aebi, P.; Steiner, U.; Abate, A. A Ga-Doped SnO2 Mesoporous Contact for UV Stable Highly Efficient Perovskite Solar Cells. J. Mater. Chem. A 2018, 6, 1850–1857. Yang, G.; Lei, H.; Tao, H.; Zheng, X.; Ma, J.; Liu, Q.; Ke, W.; Chen, Z.; Xiong, L.; Qin, P.; Reducing Hysteresis and Enhancing Performance of Perovskite Solar Cells Using Low-Temperature Processed Y-Doped SnO2 Nanosheets as Electron Selective Layers. Small 2017, 13, 1601769. Bai, Y.; Meng, X.; Yang, S. Interface Engineering for Highly Efficient and Stable Planar p-i-n Perovskite Solar Cells. Adv. Energy Mater. 2017, 8, 1701883. Wang, K.; Shi, Y.; Gao, L.; Chi, R.; Shi, K.; Guo, B.; Zhao, L.; Ma, T. W(Nb)OxBased Efficient Flexible Perovskite Solar Cells: from Material Optimization to Working Principle. Nano Energy 2017, 31, 424–431. Liu, X.; Chueh, C.-C.; Zhu, Z.; Jo, S. B.; Sun, Y.; Jen, A. K.Y. Highly Crystalline Zn2 SnO4 Nanoparticles as Efficient Electron-Transporting Layers toward Stable Inverted and Flexible Conventional Perovskite Solar Cells. J. Mater. Chem. A 2016, 4, 15294– 15301. 17 ACS Paragon Plus Environment


(55)

(56)

(57)

(58)

(59)

(60)

(61)

(62)

(63)

(64)

Deng, X.; Wilkes, G. C.; Chen, A. Z.; Prasad, N. S.; Gupta, M. C.; Choi, J. J. RoomTemperature Processing of TiOx Electron Transporting Layer for Perovskite Solar Cells. J. Phys. Chem. Lett. 2017, 8, 3206–3210. Ling, X.; Yuan, J.; Liu, D.; Wang, Y.; Zhang, Y.; Chen, S.; Wu, H.; Jin, F.; Wu, F.; Shi, G.; Room-Temperature Processed Nb2O5 as the Electron-Transporting Layer for Efficient Planar Perovskite Solar Cells. ACS Appl. Mater. Interfaces 2017, 9, 23181– 23188. Huang, A.; Lei, L.; Zhu, J.; Yu, Y.; Liu, Y.; Yang, S.; Bao, S.; Cao, X.; Jin, P. Achieving High Current Density of Perovskite Solar Cells by Modulating the Dominated Facets of Room-Temperature DC Magnetron Sputtered TiO2 Electron Extraction Layer. ACS Appl. Mater. Interfaces 2017, 9, 2016–2022. Lu, H.; Zhang, J.; Chen, J.; Liu, Q.; Gong, X.; Feng, S.; Xu, X.; Ma, W.; Bo, Z. Ternary-Blend Polymer Solar Cells Combining Fullerene and Nonfullerene Acceptors to Synergistically Boost the Photovoltaic Performance. Adv. Mater. 2016, 28, 9559– 9566. Liu, Y.; Tang, D.; Zhang, K.; Huang, P.; Wang, Z.; Zhu, K.; Li, Z.; Yuan, L.; Fan, J.; Zhou, Y.; Tuning Surface Energy of Conjugated Polymers via Fluorine Substitution of Side Alkyl Chains: Influence on Phase Separation of Thin Films and Performance of Polymer Solar Cells. ACS Omega 2017, 2, 2489–2498. Proctor, C. M.; Kim, C.; Neher, D.; Nguyen, T. Nongeminate Recombination and Charge Transport Limitations in Diketopyrrolopyrrole-Based Solution-Processed Small Molecule Solar Cells. Adv. Funct. Mater. 2013, 23, 3584–3594. Wu, R.; Yang, B.; Zhang, C.; Huang, Y.; Cui, Y.; Liu, P.; Zhou, C.; Hao, Y.; Gao, Y.; Yang, J. Prominent Efficiency Enhancement in Perovskite Solar Cells Employing Silica-Coated Gold Nanorods. J. Phys. Chem. C 2016, 120, 6996–7004. Chavhan, S.; Miguel, O.; Grande, H.-J.; Gonzalez-Pedro, V.; Sánchez, R. S.; Barea, E. M.; Mora-Seró, I.; Tena-Zaera, R. Organo-Metal Halide Perovskite-Based Solar Cells with CuSCN as the Inorganic Hole Selective Contact. J. Mater. Chem. A 2014, 2, 12754–12760. Zhang, K.; Yu, H.; Liu, X.; Dong, Q.; Wang, Z.; Wang, Y.; Chen, N.; Zhou, Y.; Song, B. Fullerenes and Derivatives as Electron Transport Materials in Perovskite Solar Cells. Sci. China Chem. 2017, 60, 144–150. Jiang, Q.; Chu, Z.; Wang, P.; Yang, X.; Liu, H.; Wang, Y.; Yin, Z.; Wu, J.; Zhang, X.; You, J. Planar-Structure Perovskite Solar Cells with Efficiency beyond 21%. Adv. Mater. 2017, 29, 1703852.


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