Numerical simulation of planar heterojunction perovskite solar cells

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Numerical simulation of planar heterojunction perovskite solar cells based on SnO2 electron transport layer peng zhao, Zhenhua Lin, Jiaping Wang, Man Yue, Jie Su, Jincheng Zhang, Jingjing Chang, and Yue Hao ACS Appl. Energy Mater., Just Accepted Manuscript • DOI: 10.1021/acsaem.9b00755 • Publication Date (Web): 24 May 2019 Downloaded from http://pubs.acs.org on May 24, 2019

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ACS Applied Energy Materials

Numerical simulation of planar heterojunction perovskite solar cells based on SnO2 electron transport layer Peng Zhao,a Zhenhua Lin,a* Jiaping Wang,a Man Yue,a Jie Su,a Jincheng Zhang,a,b Jingjing Chang, a,b* Yue Haoa,b aState

Key Discipline Laboratory of Wide Band Gap Semiconductor Technology,

Shaanxi Joint Key Laboratory of Graphene, School of Microelectronics, Xidian University, 2 South Taibai Road, Xi’an, 710071, China. E-mail: [email protected]; [email protected] bAdvanced

Interdisciplinary Research Center for Flexible Electronics, Xidian

University, Xi’an, 710071, China. Abstract The perovskite solar cells attracted great attention owing to their low cost and high performance. SnO2 as electron transport layer has been mostly used in the perovskite solar cells due to its excellent properties, such as good antireflection, suitable band edge position, and high electron mobility. In this study, the effects of band offsets, electrode work function, perovskite layer thickness and electron mobility of SnO2 were investigated on the performance of perovskite solar cells. According to the results, the power conversion efficiency (PCE) was first enlarged with the increasing thickness of perovskite layer, and then became saturated when the perovskite layer thickness was larger than 500 nm. The optimum conduction band offset (CBO=Ec_ETL- Ec_perovskite) and valence band offset (VBO=Ev_HTL- Ev_perovskite) were -0.1 ~ 0.4 eV and -0.1 ~ 0.1 eV, respectively. The optimal PCE was achieved when

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cathode electrode work function (Фcathode) was larger than -4.8 eV, and anode electrode work function (Фanode) was smaller than -5.2 eV due to increased built-in voltage and carrier extraction. Moreover, the optimal PCE can be obtained when electron mobility of SnO2 was greater than 10-3 cm2/Vs. This work would provide guidance to develop high performance perovskite solar cells. Keywords: perovskite solar cell, SnO2 electron transport layer, numerical simulation, band offset, electrode work function 1. Introduction In 2009, Miyasaka and co-workers employed CH3NH3PbI3 and CH3NH3PbBr3 as absorbers into solar cells, and power conversion efficiencies (PCEs) of 3.81 % and 3.13 % were obtained, respectively.1 Since then, lots of scientific workers devoted themselves to the research of perovskite solar cells (PSCs), and PCEs of PSCs increased rapidly from 3.81 % to 23.3 %.2–9 During the past few years, different kinds of PSC structures have been investigated, such as perovskite sensitized solar cell,9,10 mesoporous structured PSCs

2,3,11

and planar heterojunction PSCs

4,6,12.

Compared

with mesoporous structured PSCs, the preparation method of planar heterojunction PSCs is much simpler owing to the absence of high-temperature processed mesoporous layers.13 Meanwhile, planar heterojunction PSC can be combined with CIGS (CuInxGa1-xSe2) or silicon solar cell to create tandem solar cell, which could significantly improve the solar cell performance.14,15 Generally speaking, electron transport layer (ETL) and hole transport layer (HTL) are significantly important for the PSC performance, since they prevent carrier recombination in the interface.16,17


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TiO2 was usually used as ETL. However, the low mobility and high temperature processing of TiO2 limit the further improvement of the PSC performance in flexible devices.18 Thus, it is necessary to replace TiO2 with better electron transport materials with low temperature process. Compared with TiO2, SnO2 is more competent to act as ETL owing to several advantages, such as higher mobility, wider bandgap and superior optical transmittance.19–23 The higher mobility means more efficient electron transfer from perovskite to SnO2, and the superior optical transmittance means more light transmitting into absorber layer. In Snaith’s report, the stability of TiO2-based photovoltaic devices deteriorated because of oxygen vacancies and UV light induced degradation.24 In Miyasaka’s report, the deterioration of SnO2 based PSCs is slower than that of TiO2 based PSCs with the same preparation method.25 Parasitic absorption of SnO2 is small due to the large bandgap, which results in little absorption of light in SnO2 layer. Thus, SnO2 is a suitable material for ETL. Many kinds of semiconductor devices can be modeled by commercial software Silvaco TCAD, such as MOSFET, FinFET, thin-film transistor, solar cell, etc. As for solar cell, Silvaco TCAD could calculate energy bands, photogeneration rate, carrier concentration, current density – voltage (J – V) characteristic, spectral response by solving three basic equations (Poisson’s equation, carrier continuity equation and drift-diffusion equation). Thus, in this work, Silvaco TCAD was used to explore the characteristics of PSCs. Firstly, the thickness of perovskite was investigated and the optimal thickness was found. Secondly, the effects of band offset, electrode work function, SnO2 electron mobility on PSC device performance were simulated.



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Meanwhile, the physical mechanism of the effect of these parameters on the device performance was also analyzed. Our work can provide some important guidance for device design and optimization from the considerations of theory. 2. Simulation Silvaco TCAD was used in the simulation, mainly based on three basic equations: possion’s equation: ∂2𝜑 ∂𝑥

2

𝑞

(1)

= 𝜀(𝑛 ― 𝑝)

carrier continuity equation: ∂𝑛 ∂𝑡

1∂𝐽𝑛

= 𝑞 ∂𝑥 + 𝐺 ― 𝑅

∂𝑝 ∂𝑡

1∂𝐽𝑝

(2)

= ― 𝑞 ∂𝑥 + 𝐺 ― 𝑅

drift-diffusion equation: ∂𝑛

∂𝜑

∂𝑝

∂𝜑

𝐽𝑛 = 𝑞𝐷𝑛∂𝑥 - 𝑞𝜇𝑛𝑛 ∂𝑥 𝐽𝑝 = ― 𝑞𝐷𝑝∂𝑥 - 𝑞𝜇𝑝𝑝 ∂𝑥

(3)

As shown in Figure S1, planar structure FTO/SnO2/CH3NH3PbI3/Spiro-OMeTAD/Ag was used in this work. In the structure, FTO was used as front contact for planar PSC, SnO2 was employed as ETL, CH3NH3PbI3 acted as absorber layer, Spiro-OMeTAD was used as HTL, and Ag acted as metal rear contact. In Sherkar’s report, transfer-matrix method proved to be suitable for PSC device simulation.26 Thus, in the simulation, transfer-matrix method was employed as optical model to calculate carrier generation rate. As for transfer-matrix method, optical electric field was calculated first, and then carrier generation rate was obtained based on optical electric field according to Eq. (4) and Eq. (5), where 𝜀0 is vacuum permittivity, c is the speed of light, k is imaginary part of refractive index, |E(x)|2 is optical electric field, n is real part of refractive index, h is Planck constant, λ is wavelength, and G(x) is carrier


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generation

rate.

Shockley-Read-Hall

(SRH)

recombination,

band

to

band

recombination, and Auger recombination were considered.27-28 Standard AM 1.5G solar spectrum was used in PSC to get J – V curve under illumination. The electrical parameters of PSC used in our simulation are summarized in Table 1. The optical parameters of Ag were taken from Silvaco database. For FTO, CH3NH3PbI3, SnO2, and Spiro-OMeTAD, the optical parameter was obtained from literature.29 𝑄(𝑥,𝜆) =

2𝜋𝑐𝜀0𝑘𝑛|𝐸(𝑥)|2

,

𝜆

(4)

𝜆 𝜆

𝐺(𝑥) = ∫𝜆2ℎ𝑐𝑄(𝑥,𝜆)𝑑𝜆,

(5)

1

Table 1. Electrical parameters of PSC. Parameter

SnO2

CH3NH3PbI3

Spiro-OMeTA D

Thickness (nm)

30

400

200

Accept density, NA (cm-3)

-

1013

1018

Donor density, ND (cm-3)

1017

-

-

Bandgap energy, Eg (eV)

3.6 [18]

1.5 [30]

3 [31]

Electron affinity, chi (eV)

4.4 [32]

3.9 [30]

2.45 [31]

Relative dielectric permittivity, 𝜀r

9 [33]

30 [30]

3 [31]

Effective conduction band density,

4.36×1018 [34]

2.5×1020 [30]

2.5×1020 [30]

2.52×1019 [34]

2.5×1020 [30]

2.5×1020 [30]

240 [35]

50 [30]

2×10-4 [31]

Nc (cm-3) Effective valence band density, Nv (cm-3) Mobility of electron, 𝜇n (cm2/Vs)



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Mobility of hole, 𝜇p (cm2/Vs)

25 [36]

50 [30]

2×10-4 [31]

Lifetime of electron, τn (s)

2.83×10-2 [37]

10-6 [38]

10-7 [38]

Lifetime of hole, τp (s)

2.83×10-2 [37]

10-6 [38]

10-7 [38]

3. Result and discussion 3.1. Influence of thickness of perovskite layer Perovskite layer plays an important role in the device performance because it absorbs light to generate photo-generated carriers. Thus, it is necessary to explore the optimal thickness of perovskite. Figure 1(a) showed that short circuit current density (Jsc) increased rapidly when the thickness of perovskite increased from 100 nm to 500 nm. And then, Jsc almost saturated to the plateau when the thickness exceeded 500 nm. The reason of the tendency can be found in Figure 2. Figure 2(a) showed the external quantum efficiency (EQE) of PSCs with different thicknesses of perovskite layers. EQE is defined as the ratio of electrons converted by incident photons and total incident photons. In Figure 2(a), when the thickness of perovskite was smaller than 500 nm, the EQE of PSC was enhanced obviously, which meant the increase of photo absorption was significant. However, when the thickness of perovskite layer was larger than 500 nm, the EQE of PSC increased much smaller, which meant the increase of photo absorption was much smaller. The absorption of light with long wavelength increased with the increase thickness of perovskite layer. The similar situation can also be seen from Figure 2 (b), in which the increase of net carrier generation rate (carrier generation rate was subtracted by carrier recombination rate) was obvious when the thickness of perovskite was smaller than 500 nm. Net carrier


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generation rate increased much slowly when the thickness of perovskite exceeded 500 nm. The growth trend of EQE and net carrier generation rate were same as that of Jsc. As shown in Figure 1(b), open circuit voltage (Voc) dropped from 1.22 V to 1.13 V with the thickness of perovskite increasing from 100 nm to 1000 nm. Figure S2 showed the Quasi Fermi levels with various perovskite layer thicknesses. As is well known, there was a positive correlation between Voc and the difference between Quasi Fermi levels. Thus, as can be seen from Figure S2, the difference between electron Quasi Fermi level and hole Quasi Fermi level slightly decreased with the increase of perovskite layer thickness, which resulted in Voc continuously decreasing. In order to further explore the reason for perovskite layer thickness affecting the splitting of the quasi Fermi level, the carrier generation rate per unit thickness (carrier generation rate divided by perovskite layer thicknesses, see in Figure S2) was calculated. Contrary to the effect of perovskite layer thickness on net carrier generation rate, the carrier generation rate per unit thickness decreased when perovskite layer thickness increased, which meant the concentration of non-equilibrium carriers decreased as the thickness of the perovskite layer increased. As we know, a decrease in the non-equilibrium carrier concentration causes the electron and hole quasi Fermi levels to approach. Hence, carrier generation rate per unit thickness and Voc decreased in the same trend (Figure 1 (b) and S2 (a)). We could find from Figure 1(c) that fill factor (FF) almost kept constant. Finally, Figure 1(d) showed that PCE was enlarged obviously when the perovskite layer thickness was smaller than 500 nm. And then PCE almost saturated to the plateau when the thickness exceeded 500 nm. Thus, the



optimal thickness of perovskite layer was 500 nm. 25

1.24

20

Voc (V)

Jsc (mA/cm2)

(a)

15

200

400

600

800

1.20 1.16

1000

200

Thickness of perovskite (nm)

400

600

800

1000


90

25 (c)

(d)

PCE (%)

85

FF (%)

(b)

1.12 10

80 75 70

200

400

600

800

1000


20

15

10

200

400

600

800

1000


Figure 1. Variations of PSC device performance parameters with different

1.0

(a)

0.8 0.6 0.4 0.2 0.0 300

Thickness of perovskite 100 nm 300 nm 600 nm 900 nm

400

500

600

700

Wavelength (nm)

800

Net carrier generation rate (cm-2s-1)

thicknesses of perovskite: (a) Jsc, (b) Voc, (c) FF, and (d) PCE.

EQE(-)

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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1.4x1017

(b)

1.2x1017

1017

8x1016

200

400

600

800

1000


Figure 2. (a) EQE of PSCs with different perovskite layer thicknesses, and (b) net carrier generation rate with different perovskite layer thicknesses. 3.2. Influence of conduction band offset (CBO) of ETL/perovskite layer As is well known, CBO plays an important role in the performance of solar cells. Thus, in this section, we discussed the effect of CBO of ETL/perovskite layer. In order to simulate CBO of ETL/perovskite layer, IDL1 (interface defect layer 1) was


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inserted between ETL and perovskite to act as interface and the thickness of IDL1 was set to be 10 nm. As shown in Figure S3 (a), we defined that CBO was negative when chiETL was larger than chiperovskite, which means conduction band (Ec) of ETL was lower than that of perovskite. As shown in Figure S3 (b), we defined that CBO was positive when chiETL was smaller than chiperovskite, which means conduction band of ETL was higher than that of perovskite. In the case of the negative CBO, Ec_IDL1 was set to be identical to Ec_ETL, and Ev_IDL1 was set to be identical to Ev_perovskite. In the case of the positive CBO, Ec_IDL1 was set to be identical to Ec_perovskite, and Ev_IDL1 was also set to be identical to Ev_perovskite. The charge carrier lifetime of IDL1 was set to 10-8 s. The other parameters of IDL1 were set to be identical to perovskite layer. This kind of methodology has been proved in the previous report.39 In Figure 3 (a), we found that Voc monotonically increased with increasing the CBO from -0.5 to -0.1 eV, Jsc almost remained constant, and FF increased slightly (from 76.72 % to 81.36 %). J – V curves were almost coincident when the CBO increased from -0.1 to 0.4 eV. After that, the performance of PSCs decreased obviously when the CBO was larger than 0.4 eV. Figure 3 (d) showed energy band diagrams with the negative value (-0.5 eV) of CBO. There was a cliff at ETL/perovskite interface. However, the cliff did not impede the electron transfer from perovskite to ETL. Thus, Jsc almost remained constant. The activation energy for carrier recombination (Ea) was represented by Eg_perovskite -|CBO| when CBO was negative. Thus, Ea monotonically decreased with decreasing the CBO from -0.1 to -0.5 eV. Meanwhile, as shown in Figure 3 (c), recombination rate kept increasing when the CBO decreased from -0.1 to



-0.5 eV. Thus, Voc decreased when the negative CBO decreased. When the CBO was positive, Ea was equal to Eg_perovskite. However, a spike was formed at the ETL/perovskite interface (see Figure 3 (b)). When the CBO exceeded 0.4 eV, the spike impeded the photo-generated electron transfer from perovskite to ETL significantly. It resulted in Jsc and FF decreasing obviously. In Figure 3 (a), we found that Voc was almost constant when the CBO was positive, and this is because the spike impeded both photo generation current and forward current (see Eq. (6)). In Eq. (6), IL was photo generation current and Is was forward current. Thus, the optimal performance of the device (Jsc = 21.5 mA/cm2, Voc = 1.17 eV, FF = 81.37%, and PCE = 20.54%) could be obtained when CBO ranged from -0.1 to 0.4 eV. Voc =

𝑘0𝑇 𝑞

𝐼𝐿

3

(a)

0.5

0.4

0.3

HTL

0.2

1

15 -0.5 eV

10 5

-0.4 eV -0.3 eV -0.2 eV

0.6 eV

0 0.0

0.3

0.6

0.9

-2

3

(c)

2

Energy (eV)

perovskite

2x1016 CBO=-0.5 eV CBO=-0.3 eV CBO=-0.2 eV

1x1016

55

60

perovskite EV CBO 0.3 eV 0.5 eV 0.6 eV

ETL

100

200

300

400

500

600

Position in the device (nm)

Voltage (V)

IDL1

60

-1

-4

1.2

40

0

-3

4x1016

0 50

EC

0.6

2

0.5 eV

3x1016

(b)

0.7

-0.1, 0, 0.1, 0.2, 0.3, 0.4 eV

20

5x1016

(6)

ln (𝐼𝑠 +1)

Energy (eV)

Current density (mA/cm2)

25

Recombination rate (cm-3s-1)

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

Page 10 of 27

65


70

(d)

EC

1 perovskite

0

EV

-1 -2

IDL1

-3

SnO2

-4

100

Spiro-OMeTAD 200

300

400

500

600


Figure 3. (a) J – V curves of the PSCs with different CBOs, and (b) energy band


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diagrams of PSCs with different positive values of CBOs. (c) Recombination rate in the device with different negative CBOs, and (d) energy band diagrams of the device with negative value (-0.5 eV) of CBO. 3.3. Influence of valence band offset (VBO) of perovskite/HTL layer Similar to CBO, VBO plays an important role in the performance of solar cells as well. In order to simulate VBO of perovskite/HTL layer, IDL2 (interface defect layer 2) was inserted between HTL and perovskite to act as interface and the thickness of IDL2 was set to be 10 nm. In Figure S4, we defined VBO was negative when Ev_HTL was higher than Ev_perovskite, and VBO was positive when Ev_HTL was lower than Ev_perovskite. In the case of the negative VBO, Ev_IDL2 was set to be identical to Ev_HTL. In the case of the positive VBO, Ev_IDL2 was set to be identical to Ev_perovskite. The charge carrier lifetime of IDL2 was set to 10-8 s. The other parameters of IDL2 were set to be identical to perovskite layer. Figure 4 (a) showed J – V curves of the PSCs with different VBOs. Voc increased obviously with the VBO increasing from -0.5 to -0.1 eV, FF increased slightly, and Jsc almost remained constant. The reason of the results could be found in Figure 4 (c)-(d). Figure 4 (d) showed that energy band diagrams of the device with negative value (-0.4 eV) of VBO. There was a cliff at perovskite/HTL interface; however, the cliff did not impede the photo-generated hole transfer from perovskite layer to HTL. Thus, Jsc almost remained constant. The activation energy for carrier recombination (Ea) was represented by Eg_perovskite -|VBO| when VBO was negative. Thus, Ea monotonically increased with increasing the VBO from -0.5 to -0.1 eV. Meanwhile, in Figure 4 (c), the recombination rate of IDL2



decreased obviously with the VBO increasing from -0.5 to -0.1 eV, which made Voc increase. J – V curves almost overlapped when the VBO increased from -0.1 to 0.1 eV. And then, when the VBO was larger than 0.1 eV, the performance of the device dropped significantly. As shown in Figure 4 (b), the spike increased with increasing VBO from 0.1 to 0.3 eV, which impeded photo-generated carrier transfer from perovskite layer to HTL. What’s more, the slope of energy band of perovskite layer decreased with the increase of VBO, which resulted in the decrease of the electric field across perovskite layer. Perovskite layer changed from complete depletion to incomplete depletion and the photo-generated carriers could not be fully extracted. It resulted in Jsc and FF decreasing obviously. Thus, the optimal performance of the device (Jsc = 21.5 mA/cm2, Voc = 1.17eV, FF = 80.88%, and PCE = 20.42%) could be obtained when VBO ranged from -0.1 to 0.1 eV.


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Page 13 of 27

3

(a)

-0.1 eV, 0 eV, 0.1 eV

20

2

0.2 eV

15

-0.5 eV -0.4 eV

10

-0.3 eV

0.3 eV

-0.2 eV

5

0.2

0.4

0.6

0.8

1.0

2

VBO=-0.2 eV VBO=-0.4 eV VBO=-0.5 eV

perovskite

ETL

100

200

300

IDL2

5.0x1017

(d)

455

460

500

600

465

470


EC

Spiro-OMeTAD

1 0

perovskite

EV

-1 -2

SnO2

IDL2

-3 0.0 450

400

Position in the device (nm) 3

Energy (eV)

1.0x1018

VBO 0.1 eV 0.2 eV 0.3 eV

-2

-4

1.2

(c)

1.5x1018

HTL

-1

Voltage (V) 2.0x1018

perovskite

0

-3

0 0.0

(b)

1

Energy (eV)


25


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


-4

100

200

300

400

500

600


Figure 4. (a) J – V curves of the PSCs with different VBOs, and (b) energy band diagrams of PSCs with different positive values of VBOs. (c) Recombination rate in the devices with different negative VBOs, and (d) energy band diagrams of the device with negative value (-0.4 eV) of VBO. 3.4. Influence of anode electrode work function In the device, anode electrode work function (Фanode) influenced energy band diagrams of PSCs and further influenced the extraction of carriers of perovskite layer. Thus, it was meaningful to explore the effect of Фanode on the performance of PSCs. Figure 5 (a) showed J – V curves of PSCs with different Фanode. In order to avoid the influence of cathode electrode work function (Фcathode), the contact between ETL and cathode electrode was set to ohmic contact. As shown in Figure 5 (a), the performance of the device monotonically increased with decreasing Фanode from -4.2 to -5.2 eV.



This is because the slope of energy band of perovskite layer increased with the Фanode decreasing from -4.2 to -5.2 eV (Figure 5 (b)), which increased built-in voltage and further increased electric field across the perovskite layer. The increased electric field led to perovskite layer changing from incomplete depletion to complete depletion and extracting the carriers of perovskite layer more efficiently. Figure 5 (c)-(d) showed that with decreasing Фanode from -4.2 to -5.2 eV, electron and hole concentration distributions of the perovskite layer decreased because the extraction of carriers of perovskite layer was more efficient. J – V curves were overlapped when Фanode decreased from -5.2 to -5.4 eV. This is because energy bands were overlapped for Фanode=-5.2 to -5.4 eV, which resulted in electric field across the perovskite layer remaining unchanged. Thus, the extraction of carriers remained unchanged, as shown in Figure 5 (c)-(d). Consequently, the performance of PSC was optimal (Jsc = 21.5 mA/cm2, Voc = 1.17eV, FF = 80.85%, and PCE = 20.40%) when Фanode was smaller than -5.2 eV.


Page 14 of 27

Page 15 of 27

3

15

- 5 eV

- 4.8 eV

5

- 4.6 eV

10

.4 eV - 5.2~-5

20

Energy (nm)

(a)

- 4.4 eV


25

- 4.2 eV 0.2

0.4

0.6

0.8

1.0

-2

1020

(c) -4.2 eV

1016 10

15

1014

-4.4 eV

1013

-4.6 eV

1012 10

11

10

10

-4.8 eV -5 eV 100

-5.2~-5.4 eV 200

300

eV

.2~ -5

.4 e

V

HTL

perovskite SnO2 100

200

300

400

500

600


Hole concentration (cm-3)

10

17

-5

-1

-4

1.2

-5

0

-3

0 0.0

(b)

24.2 4.6 e V eV 1

Voltage (V)

Electron concentration (cm-3)

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


400

Position in the perovskite layer (nm)

10

18

10

16

1014 10

12

10

10

(d) -4.6 eV

-4.8

-4.4 eV

-4.2 eV

eV

-5

eV

.4

-5 2~ 5.

eV

100

200

300

400


Figure 5. (a) J – V curves of the PSCs with different Фanode, and (b) energy band diagrams of the devices with different Фanode. (c) Electron and (d) hole concentration distributions of the perovskite layers with various Фanode. 3.5. Influence of cathode electrode work function In the above analysis, we found that anode electrode work function played an important role in the performance of PSCs. Correspondingly, cathode electrode work function should be an important factor affecting the performance of PSCs as well. Thus, cathode electrode work function was explored in this section. In order to avoid the influence of anode electrode work function, the contact between HTL and anode electrode was set to ohmic contact. Figure 6 (a) showed J – V curves of PSCs with different Фcathode. As shown in Figure 6 (a), the performance of PSCs monotonically decreased with Фcathode decreasing from -4.8 to -6.1 eV. The result could be explained



by Figure 6 (b). Figure 6 (b) showed energy band diagrams of the device with different Фcathode. In Figure 6 (b), the slope of energy band of perovskite layer decreased with the Фcathode decreasing from -4.8 to -5.4 eV, which decreased built-in voltage and further decreased electric field across the perovskite layer. The decreased electric field led to perovskite layer changing from complete depletion to incomplete depletion and extracting the carriers of perovskite layer less efficiently. What’s more, with decreasing Фcathode from -5.4 to -6.1 eV, a spike was formed at the interface between ETL and perovskite, indicated by the dashed rectangle in Figure 6 (b). The spike could even impede the transport of the photo-generated carriers. With decreasing Фanode from -4.8 to -6.1 eV, electron and hole concentration distributions of the perovskite layer increased because of the less efficient extraction of the photo-generated carriers and the spike at the interface. With the decrease of Фcathode from -4.4 to -4.8 eV, J – V curves were overlapped, since energy bands were overlapped when Фcathode decreased from -4.4 to -4.8 eV, as shown in Figure 6 (b). Thus, the extraction of photo-generated carriers remained unchanged. Electron and hole concentration distributions of the perovskite layer were also overlapped with decreasing Фcathode from -4.4 to -4.8 eV (Figure 6 (c)-(d)). Consequently, the optimal performance of PSC (Jsc = 21.5 mA/cm2, Voc = 1.17eV, FF = 81.13%, and PCE = 20.47%) could be obtained when Фcathode was larger than -4.8 eV.


Page 16 of 27

Page 17 of 27

3

(a)

- 4.8~- 4.4 eV

Energy (eV)

- 5 eV

- 5.2 eV

5

- 5.6 eV

10

- 5.4 eV

15

(b)

2

20

- 5.8 eV


25

- 6.1 eV

HTL

1

perovskite - 5.2 eV - 5 eV

0 -1

- 4.8~- 4.4 eV ETL - 6.1 eV - 5.8 eV - 5.6 eV - 5.4 eV

-2 -3

0 0.0

0.2

0.4

0.6

0.8

1.0

100

1.2

Voltage (V) 1017

1020

(c)

- 6.1 eV

1015

10

13

- 5.8 eV - 5.6 eV - 5.4 eV - 5.2 eV

1011 - 5 eV 10

- 4.8~- 4.4 eV

9

100

200

300

200

300

400

500

600


400

Hole concentration (cm-3)

Electron concentration (cm-3)

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


10

18

(d)

- 5.8 eV - 5.6 eV

- 6.1 eV

- 5.4 eV

1016 - 5.2 eV 1014

-5e

-

1012 1010


.4

V

100

200

-4 8~ . 4

300

eV

400


Figure 6. (a) J – V curves of the devices with different Фcathode, and (b) energy band diagrams of the devices with different Фcathode. (c) Electron and (d) hole concentration distributions of the perovskite layers with various Фcathode. 3.6. Influence of electron mobility of SnO2 layer As is well-known, electron mobility of SnO2 is much greater than that of TiO2. High carrier mobility is beneficial to the extraction of carrier by electrode. As shown in Figure 7, device parameters (Jsc, Voc, FF, PCE) increased first and then tended to saturate. This is because the recombination rate was larger when electron mobility of SnO2 was smaller than 10-4 cm2/Vs, which resulted in low Jsc and FF, as shown in Figure 8 (a). After that, recombination rate tended to saturate (electron mobility of SnO2 > 10-4 cm2/Vs), Jsc and FF tended to saturate as well. The change trend of recombination rate was the same as that of Jsc and FF, and the optimal Jsc was 21.5



mA/cm2, the optimal FF was 81.12%. As for Voc, we could find in Figure 8 (b) that the slope of energy band of perovskite layer increased with increasing electron mobility of SnO2 from 10-7 to 10-5 cm2/Vs. Thus, electric field increased as well. As a result, photo-generated carrier could be fully extracted. Thus, Voc increased with increasing electron mobility of SnO2 from 10-7 to 10-5 cm2/Vs. And then, energy band was overlapped when electron mobility of SnO2 exceeded 10-5 cm2/Vs. Consequently, Voc saturated to plateau (1.17 V). In summary, the optimal performance of the device could be obtained when electron mobility of SnO2 exceeded 10-3 cm2/Vs, and the optimal PCE was 20.43 %.

20

1.20

(a)

16 12

1.12 1.08

8 4

(b)

1.16

VOC (V)

JSC (mA/cm2)

24

10-6

10-4

10-2

100

1.04

102

10-6

10-4

10-2

100

102

Electron mobility of SnO2 (cm2/Vs)

2

Electron mobility of SnO2 (cm /Vs) 80 (c)

20 (d)

PCE (%)

FF (%)

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

Page 18 of 27

60 40 20

15 10 5 0

10

-6

10

-4

10

-2

10

0

10 2

2

Electron mobility of SnO2 (cm /Vs)

10-6

10-4

10-2

100

102

Electron mobility of SnO2 (cm2/Vs)

Figure 7. Variations of PSC device performance parameters with different electron mobilities of SnO2: (a) Jsc, (b) Voc, (c) FF, and (d) PCE.


1.2x1017

3

(a)

2

Energy (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



Page 19 of 27

9.0x1016

6.0x1016

-6 2 10-7 cm2/Vs 10 cm /Vs

HTL

1 perovskite

0 -1 -2

3.0x1016

(b)

10-5~102 cm2/Vs ETL

-3 10-6

10-4

10-2

100

102 2

Electron mobility of SnO2 (cm /Vs)

100

200

300

400

500

600


Figure 8. (a) Recombination rate as a function of electron mobility of SnO2, and (b) energy band diagrams with various electron mobilities of SnO2. 4. Conclusion In this study, planar structure FTO/SnO2/CH3NH3PbI3/Spiro-OMeTAD/Ag was employed owing to the high carrier mobility of SnO2, and some factors which affected the performance of PSCs obviously were explored. According to the results, the optimal performance of the device could be obtained when the perovskite layer thickness achieved 500 nm, and the suitable value of CBO was -0.1 to 0.4 eV. When the conduction band of ETL was lower than that of perovskite layer, interface recombination increased significantly. On the contrary, when conduction band of ETL was too high, the spike impeded the transport of photo-generated carrier. The optimum VBO was -0.1 to 0.1 eV. When valence band of HTL was higher than that of perovskite layer, the reason was similar to that of CBO. In contrast, incomplete depletion of perovskite layer and the spike were harmful to the extraction and transport of photo-generated carrier. As for electrode work function, because of the change of energy band, the optimal performance could be obtained when Фanode (Фcathode) was smaller (greater) than -5.2 eV (-4.8eV). In addition, electron mobility of



SnO2 was investigated as well. In order to achieve excellent device performance, the quality of SnO2 should be improved to obtain high electron mobility of SnO2. Our work could provide some important guidance for device design and optimization from the consideration of theory. Acknowledgements This work was financially support by National Natural Science Foundation of China (61604119, 61704131, and 61804111), and Young Elite Scientists Sponsorship Program by CAST (2016QNRC001). References (1)

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.

(2)

Kim, H. S.; Lee, C. R.; Im, J. H.; Lee, K. B.; Moehl, T.; Marchioro, A.; Moon, S. J.; Humphry-Baker, R.; Yum, J. H.; Moser, J. E.; Grätzel, M.; Park, N. G. Lead Iodide Perovskite Sensitized All-Solid-State Submicron Thin Film Mesoscopic Solar Cell with Efficiency Exceeding 9%. Sci. Rep. 2012, 2, 591.

(3)

Lee, M. M.; Teuscher, J.; Miyasaka, T.; Murakami, T. N.; Snaith, H. J. Efficient Hybrid Solar Cells Based on Meso-Superstructured Organometal Halide Perovskites. Science 2012, 338, 643–647.

(4)

Chang, J.; Lin, Z.; Zhu, H.; Isikgor, F. H.; Xu, Q.-H.; Zhang, C.; Hao, Y.; Ouyang, J. Enhancing the Photovoltaic Performance of Planar Heterojunction Perovskite Solar Cells by Doping the Perovskite Layer with Alkali Metal Ions.


Page 20 of 27

Page 21 of 27 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


J. Mater. Chem. A 2016, 4, 16546–16552. (5)

Liu, Z.; Chang, J.; Lin, Z.; Zhou, L.; Yang, Z.; Chen, D.; Zhang, C.; Liu, S. F.; Hao, Y. High-Performance Planar Perovskite Solar Cells Using Low Temperature, Solution-Combustion-Based Nickel Oxide Hole Transporting Layer with Efficiency Exceeding 20%. Adv. Energy Mater. 2018, 8, 1703432.

(6)

Zhou, H.; Chen, Q.; Li, G.; Luo, S.; Song, T.; Duan, H.; Hong, Z.; You, J.; Liu, Y.; Yang, Y. Interface engineering of highly efficient perovskite solar cells, Science. 2014, 345, 542-546.

(7)

Jeon, N. J.; Noh, J. H.; Yang, W. S.; Kim, Y. C.; Ryu, S.; Seo, J.; Seok, S. Il. Compositional Engineering of Perovskite Materials for High-Performance Solar Cells. Nature 2015, 517, 476–480.

(8)

Chang, J.; Zhu, H.; Li, B.; Isikgor, F. H.; Hao, Y.; Xu, Q.; Ouyang, J. Boosting the Performance of Planar Heterojunction Perovskite Solar Cell by Controlling the Precursor Purity of Perovskite Materials. J. Mater. Chem. A 2016, 4, 887– 893.

(9)

Burschka, J.; Pellet, N.; Moon, S.-J.; Humphry-Baker, R.; Gao, P.; Nazeeruddin, M. K.; Grätzel, M. Sequential Deposition as a Route to High-Performance Perovskite-Sensitized Solar Cells. Nature 2013, 499, 316– 319.

(10)

Im, J.-H.; Lee, C.-R.; Lee, J.-W.; Park, S.-W.; Park, N.-G. 6.5% Efficient Perovskite Quantum-Dot-Sensitized Solar Cell. Nanoscale 2011, 3, 4088.

(11)

Wang, K. C.; Jeng, J. Y.; Shen, P. S.; Chang, Y. C.; Diau, E. W. G.; Tsai, C.



H.; Chao, T. Y.; Hsu, H. C.; Lin, P. Y.; Chen, P.; Guo, T. F.; Wen, T. C. P-Type Mesoscopic Nickel Oxide/Organometallic Perovskite Heterojunction Solar Cells. Sci. Rep. 2014, 4, 4756. (12)

Zhou, L.; Chang, J.; Liu, Z.; Sun, X.; Lin, Z.; Chen, D.; Zhang, C.; Zhang, J.; Hao, Y. Enhanced Planar Perovskite Solar Cell Efficiency and Stability Using a Perovskite/PCBM Heterojunction Formed in One Step. Nanoscale 2018, 10, 3053–3059.

(13)

Chang, J.; Zhu, H.; Xiao, J.; Isikgor, F. H.; Lin, Z.; Hao, Y.; Zeng, K.; Xu, Q. H.; Ouyang, J. Enhancing the Planar Heterojunction Perovskite Solar Cell Performance through Tuning the Precursor Ratio. J. Mater. Chem. A 2016, 4, 7943–7949.

(14)

McMeekin, D. P.; Sadoughi, G.; Rehman, W.; Eperon, G. E.; Saliba, M.; Horantner, M. T.; Haghighirad, A.; Sakai, N.; Korte, L.; Rech, B.; Johnston, M. B.; Herz, L. M.; Snaith, H. J. Support-A Mixed-Cation Lead Halide Perovskite Absorber for Tandem Solar Cells. Science 2016, 351, 151–155.

(15)

Bailie, C. D.; Christoforo, M. G.; Mailoa, J. P.; Bowring, A. R.; Unger, E. L.; Nguyen, W. H.; Burschka, J.; Pellet, N.; Lee, J. Z.; Grätzel, M.; Noufi, R.; Buonassisi, T.; Salleo, A.; McGehee, M. D. Semi-Transparent Perovskite Solar Cells for Tandems with Silicon and CIGS. Energy Environ. Sci. 2015, 8, 956– 963.

(16)

Yan, W.; Li, Y.; Li, Y.; Ye, S.; Liu, Z.; Wang, S.; Bian, Z.; Huang, C. High-Performance Hybrid Perovskite Solar Cells with Open Circuit Voltage


Page 22 of 27

Page 23 of 27 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


Dependence on Hole-Transporting Materials. Nano Energy 2015, 16, 428–437. (17)

Zhao, Z.; Sun, W.; Li, Y.; Ye, S.; Rao, H.; Gu, F.; Liu, Z.; Bian, Z.; Huang, C. Simplification of Device Structures for Low-Cost, High-Efficiency Perovskite Solar Cells. J. Mater. Chem. A 2017, 5, 4756–4773.

(18)

Ma, J.; Guo, X.; Zhou, L.; Lin, Z.; Zhang, C.; Yang, Z.; Lu, G.; Chang, J.; Hao, Y. Enhanced Planar Perovskite Solar Cell Performance via Contact Passivation of TiO2/Perovskite Interface with NaCl Doping Approach. ACS Appl. Energy Mater. 2018, 1, 3826–3834.

(19)

Zhou, L.; Guo, X.; Lin, Z.; Ma, J.; Su, J.; Hu, Z.; Zhang, C.; Liu, S. (Frank); Chang, J.; Hao, Y. Interface Engineering of Low Temperature Processed All-Inorganic CsPbI2Br Perovskite Solar Cells toward PCE Exceeding 14%. Nano Energy 2019, 60, 583–590.

(20)

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.

(21)

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 Planar-Structure HC(NH2)2PbI3-Based Perovskite Solar Cells. Nat. Energy 2016, 2, 16177.

(22)

G. Yang, C. Chen, F. Yao, Z. Chen, Q. Zhang, X. Zheng, J. Ma, H. Lei, P. Qin, L. Xiong, W. Ke, G. Li, Y. Yan, G. Fang. Effective Carrier‐Concentration Tuning of SnO2 Quantum Dot Electron‐Selective Layers for High‐Performance



Page 24 of 27

Planar Perovskite Solar Cells. Adv. Mater. 2018, 30, 1706023. (23)

G. Yang, C. Wang, H. Lei, X. Zheng, P. Qin, L. Xiong, X. Zhao, Y. Yan, G. Fang. Interface engineering in planar perovskite solar cells: energy level alignment, perovskite morphology control and high performance achievement. J. Mater. Chem. A. 2017, 5, 1658-1666.

(24)

Leijtens, T.; Eperon, G. E.; Pathak, S.; Abate, A.; Lee, M. M.; Snaith, H. J. Overcoming

Ultraviolet

Light

Instability

of

Sensitized

TiO₂

with

Meso-Superstructured Organometal Tri-Halide Perovskite Solar Cells. Nat. Commun. 2013, 4, 2885. (25)

Song, J.; Zheng, E.; Bian, J.; Wang, X.-F.; Tian, W.; Sanehira, Y.; Miyasaka, T. Low-Temperature SnO2-Based Electron Selective Contact for Efficient and Stable Perovskite Solar Cells. J. Mater. Chem. A 2015, 3, 10837–10844.

(26)

Sherkar, T. S.; Momblona, C.; Gil-Escrig, L.; Bolink, H. J.; Koster, L. J. A. Improving Perovskite Solar Cells: Insights From a Validated Device Model. Adv. Energy Mater. 2017, 7, 1602432.

(27)

Zhao, P.; Liu, Z.; Lin, Z.; Chen, D.; Su, J.; Zhang, C.; Zhang, J.; Chang, J.; Hao, Y. Device Simulation of Inverted CH3NH3PbI3−xClx Perovskite Solar Cells Based on PCBM Electron Transport Layer and NiO Hole Transport Layer. Sol. Energy 2018, 169, 11–18.

(28)

Zhao, P.; Yue, M.; Lei, C.; Lin, Z.; Su, J.; Chen, D.; Zhang, C.; Zhang, J.; Chang, J.; Hao, Y. Device Simulation of Organic–Inorganic Halide Perovskite/Crystalline Silicon Four-Terminal Tandem Solar Cell With Various


Page 25 of 27 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


Antireflection Materials. IEEE J. Photovoltaics 2018, 8, 1685–1691. (29)

Burkhard, G. F.; Hoke, E. T.; McGehee, M. D. Accounting for Interference, Scattering, and Electrode Absorption to Make Accurate Internal Quantum Efficiency Measurements in Organic and Other Thin Solar Cells. Adv. Mater. 2010, 22, 3293–3297.

(30)

Pandey, R.; Chaujar, R. Technology Computer Aided Design of 29.5% Efficient Perovskite/Interdigitated Back Contact Silicon Heterojunction Mechanically Stacked Tandem Solar Cell for Energy-Efficient Applications. J. Photonics Energy 2017, 7, 022503.

(31)

Nakanishi, A.; Takiguchi, Y.; Miyajima, S. Device Simulation of CH3NH3PbI3

Perovskite/Heterojunction

Crystalline

Silicon

Monolithic

Tandem Solar Cells Using an n-Type a-Si:H/p-Type Μc-Si1-xOX:H Tunnel Junction. Phys. Status Solidi 2016, 6, 1997. (32)

Yang, G.; Lei, H.; Tao, H.; Zheng, X.; Ma, J.; Liu, Q.; Ke, W.; Chen, Z.; Xiong, L.; Qin, P.; Chen, Z.; Qin, M.; Lu, X.; Yan, Y.; Fang, G. 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.

(33)

Van Daal, H. J. The Static Dielectric Constant of SnO2. J. Appl. Phys. 1968, 39, 4467–4469.

(34)

Sanon, G.; Rup, R.; Mansingh, A. Band-Gap Narrowing and Band-Structure in Degenerate Tin Oxide (SnO2) Films. Phys. Rev. B 1991, 44, 5672–5680.



(35)

Xie, J.; Huang, K.; Yu, X.; Yang, Z.; Xiao, K.; Qiang, Y.; Zhu, X.; Xu, L.; Wang, P.; Cui, C.; Yang, D. Enhanced Electronic Properties of SnO2 via Electron Transfer from Graphene Quantum Dots for Efficient Perovskite Solar Cells. ACS Nano 2017, 11, 9176-9182.

(36)

Kanevce, A.; Gessert, T. A. Optimizing CdTe Solar Cell Performance : Impact of Variations in Minority-Carrier Lifetime and Carrier Density Profile. J. Photovoltaics 2011, 1, 99–103.

(37)

Wijeratne, K.; Akilavasan, J.; Thelakkat, M.; Bandara, J. Enhancing the Solar Cell Efficiency through Pristine 1-Dimentional SnO2 Nanostructures: Comparison of Charge Transport and Carrier Lifetime of SnO2 Particles vs. Nanorods. Electrochim. Acta 2012, 72, 192–198.

(38)

Almosni, S.; Cojocaru, L.; Li, D.; Uchida, S.; Kubo, T.; Segawa, H. Tunneling-Assisted Trapping as One of the Possible Mechanisms for the Origin of Hysteresis in Perovskite Solar Cells. Energy Technol. 2017, 5, 1767–1774.

(39)

Minemoto, T.; Julayhi, J. Buffer-Less Cu(In,Ga)Se2 Solar Cells by Band Offset Control Using Novel Transparent Electrode. Curr. Appl. Phys. 2013, 13, 103–106.


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Table of Contents (TOC) graphic 3

25

0.6

2

20

0.4

HTL

0.2

1

Energy (eV)

15 -0.5 eV

10

0 0.0

0.5

0.3

0.5 eV

5

EC

0.7

-0.1, 0, 0.1, 0.2, 0.3, 0.4 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


0.6 eV

0.3

-0.4 eV -0.3 eV -0.2 eV 0.6

0

1.2

60

perovskite EV

-1 -2 -3

0.9

40

-4

Voltage (V)


CBO 0.3 eV 0.5 eV 0.6 eV

ETL

100

200

300

400

500

600


Numerical simulation of planar heterojunction perovskite solar cells

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