Improvement in performance of lead free inverted perovskite solar cell by optimization of solar parameters

Accepted Manuscript Title: Improvement in Performance of Lead Free Inverted Perovskite Solar cell by Optimization of Solar Parameters Authors: Himanshu Dixit, Deepak Punetha, Saurabh Kumar Pandey, Member, IEEE PII: DOI: Reference:

S0030-4026(18)31773-X https://doi.org/10.1016/j.ijleo.2018.11.028 IJLEO 61875

To appear in: Received date: Accepted date:

5 October 2018 12 November 2018

Please cite this article as: Dixit H, Punetha D, Pandey SK, Improvement in Performance of Lead Free Inverted Perovskite Solar cell by Optimization of Solar Parameters, Optik (2018), https://doi.org/10.1016/j.ijleo.2018.11.028 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Improvement in Performance of Lead Free Inverted Perovskite Solar cell by Optimization of Solar Parameters aElectronics bIndian

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Himanshu Dixita*, Deepak Punethab, Saurabh Kumar Pandeyb Member, IEEE

Engineering Department, Rajasthan Technical University, Kota 324009, Rajasthan, India Institute of Technology Patna, Bihta 801103, Bihar, India

*Corresponding

author: Tel.: +91-977-200-9957 Email: [email protected]

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Abstract—Tin based perovskite FASnI3 is an excellent absorber material to achieve high power conversion efficiency (PCE) at low cost for photovoltaic utilities. It is essential to realize how solar cell parameters like doping concentration (NA), defect density (Nt), band gap (Eg), operating temperature and thickness influence the performance of photovoltaic device. In this study we have reported the perovskite solar cell (PSC) model with novel inverted architecture Glass / FTO / NiO / FASnI3 / C60 / Au using device simulation tool. FASnI3 is feasible material because of its narrower band gap and broad absorption spectrum as compare to its lead based counterpart. By optimized parameters we obtained power conversion efficiency (PCE) 9.99%, open circuit voltage (VOC) 0.97 V, short circuit current density (JSC) 25.95 mA/cm2 and fill factor (FF) 80.85% which are much improved parameters for FASnI3 as compare to available in literature. This model allows researchers to characterize fundamental solar cell parameters to obtain high performance of photovoltaic devices.

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Keywords— Absorber layer, Device simulation, Electron transport layer, Hole transport layer, Perovskite solar cell.

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1. INTRODUCTION

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In short span of period perovskite solar cells have achieved remarkable power conversion efficiency from 3.8% in 2009 to 22.7% in 2017 [1]. Strong light absorption, low temperature processing, long diffusion length, cost effectiveness etc. appreciable characteristics are there in perovskite materials that is why researches are much more interested in these type of solar cells as compare to tradition solar cells [2]. Organic-Inorganic perovskite material is used as absorber layer in solar cell with planar heterojunction architecture to harvest the light photons [3]. Methyl ammonium lead iodide (MAPbI3) is a vastly used perovskite material in photovoltaic applications but due to toxicity of Lead (Pb), many health and environmental issues are there so still Pb based perovskite solar cells are not fully commercialized [4]. To overcome these non-essential disputes, Pb is replaced with Sn based perovskite materials. Both Sn and Pb are in same group that is why both have approximately same optical and electronic characteristics so it is the best alternate we have for lead [5]. Formamidinium tin iodide (FASnI3) possesses narrower band gap (1.41eV) so it covers wide band of visible spectrum and improves photovoltaic performance. The dominant issue is rapid degradation of tin based perovskite absorber layer in ambient condition that needs to be resolved. Pb2+ is stable in this oxidation state at room temperature but Sn2+ is unstable and highly prone to oxidize into much stable state i.e. Sn 4+ and it results in low PCE and poor performance, this phenomena is known as self-doping process which is undesirable [5]. Both MASnI3 (Methyl ammonium tin iodide) and FASnI3 are susceptive to oxidation so necessary steps are taken to reduce or eliminate this unwished self-doping process. Self-doping lowers the performance of photovoltaic devices. Generally tin halides (SnX2, X= Cl, Br, I) additives are used to enhance the stability [6]. Although along with SnX2, hypo phosphorous acid, hydrazine, pyrazine can also be applied as Sn4+ inhibitor [7]. By appropriate fabrication and encapsulation stability of tin based perovskite solar cells can be improved precisely. In this paper inorganic nickel oxide (NiO) and organic fullerene (C60) utilized as hole transporting material (HTM) and electron transporting material (ETM) respectively and FASnI 3 as perovskite material. DMF (Dimethylformamide) and DMSO (Dimethyl sulfoxide) polar solvents are preferable to synthesize the perovskite thin film and to enhance the properties of HTM. These polar solvents disable pin holes in perovskite thin film and improve the uniformity of absorber layer. Band gap of lead free perovskites can be tuned between 1.3eV to 2.15eV. Till date, very few investigations have been done with the FASnI3 based perovskite solar cells and no considerable comparative studies have been reported in literature. FASnI3 is an excellent choice as light harvesting material because it possesses low band gap (1.41eV) which is next to Shockley-Queisser limit i.e. 1.34eV then its counterpart formamidinium tin iodide (FAPbI3) which has band gap of 1.47eV. Here adverse to regular structure, n-i-p inverted structure is employed. There is almost none J-V hysteresis in inverted devices along with this, easy and economical fabrication is feasible in this architecture [8-10]. Device simulation is done for Glass / FTO / NiO / FASnI3 / C60 / Au inverted

structure with parameters of each layer using simulation software and results are analysed under an AM1.5G solar spectrum at 1000W/m2 [10].

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In the fig 1 (a) energy band diagram for FASnI3 based perovskite solar cell with inverted structure is shown. NiO is used as hole transporting material and C60 is used as electron transporting material. Highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) levels are figured out for both ETM and HTM by available literature. LUMO level of C60 matches with the conduction band minimum of absorber layer so efficient electron transport will happen from FASnI 3 to Au electrode. HOMO level of C60 is also lesser than that of valance band maximum of perovskite so there will be no hole transportation from FASnI3 i.e. holes will be blocked effectively. In this way charge recombination at interface will be prevented and photovoltaic performance will be improved. Bathocuproine (BCP) buffer layer can also be used with this architecture to enhance the contacts between C60 and Au electrode. NiO which is used as HTM, transports holes from perovskite absorber layer to fluorine doped tin oxide (FTO). 2. DEVICE ARCHITECTURE AND SIMULATION

SCAPS-1D is a solar cell simulation program used to simulate the photovoltaic structures by utilizing Poisson's equation and continuity equation of charge carriers [4-6]. Tin based inverted planar heterojunction perovskite solar cell is used in this simulation work which comprises following structure: Glass substrate / FTO / NiO / FASnI 3 / C60 / Au. Lead free perovskite FASnI3 is used as an absorber layer, NiO as HTM, C60 as ETM and FTO as transparent conducting oxide. Poisson's equation for semiconductor can be inscribed as: 𝑞 ∇2 𝜓 = (𝑛 − 𝑝 + 𝑁𝐴 − 𝑁𝐷 )

(1)

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𝜖

𝜕𝑡 𝜕𝑝 𝜕𝑡

= −𝑞𝑅

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∇. 𝐽𝑝 + 𝑞

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where NA is the acceptor concentration, ND is the donor concentration and ψ is the electrostatic potential. Continuity equation for semiconductor can be written as: 𝜕𝑛 ∇. 𝐽𝑛 − 𝑞 = +𝑞𝑅 (2) (3)

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Jn is the current density for electrons, JP is the current density for holes and R is the rate of carrier recombination. There are two general effects which conduct current flow in semiconductor. First, drift of carriers because of the influence of electric field, second, diffusion current because of concentration gradient. Drift-Diffusion Current Relations: 𝐽𝑛 = 𝑞𝑛µ𝑛 𝐸 + 𝑞𝐷𝑛 ∇𝑛 (4) 𝐽𝑝 = 𝑞𝑝µ𝑝 𝐸 − 𝑞𝐷𝑝 ∇𝑝 (5)

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where DP is the diffusion coefficient for holes and Dn is the diffusion coefficient for electrons. Device simulation software extricates these basic semiconductor equations and shows the simulation results. A planar heterojunction perovskite solar cell (PSC) structure is shown in the fig. 2. In any photovoltaic device there are three main parts: Light absorber layer to convert incident light photons into charge carriers i.e. electrons and holes, carrier collector to capture the carriers and metal contacts to transfer charge carriers to external circuity [11]. FASnI3 acts as a p-type perovskite because unstable Sn2+ oxidation state oxidizes into more stable Sn4+ state at ambient conditions so in absorber layer p-type concentration increases, this is also known as self-doping process and it enhances undesirable recombination. This should be avoided to achieve high photovoltaic performance [12]. Simulation parameters used in this work for all layers are displayed in table 1.

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Zonglong Zhu et al. [13] worked with ITO/SnO 2/C60/FASnI3/Spiro-OMeTAD/Ag and obtained VOC 0.47 volt, JSC 22.45 mA/cm2, FF 67.8% and PCE 7.09%. Weiqiang Liao et al. [14] worked experimental work with Ag/BCP/C 60/FASnI3/PEDOT: PSS/ITO inverted planar heterojunction architecture and achieved the following parameters: V OC 0.465 volt, JSC 22.07 mA/cm2, FF 60.67%, PCE 6.22%. Tze-Bin Song et al. [15] used CuI as hole transporting material with tin halide perovskite (FASnI 3 and CsSnI3) and achieved VOC 0.38 volt, JSC 25.71 mA/cm2, FF 49.05% and PCE 4.81%. Chenxin Ran et al. [16] worked on 2D-3D bulk heterojunction FASnI3 and achieved VOC 0.47 volt, JSC 20.07 mA/cm2, FF 74% and PCE 6.98%. Efat Jokar et al. [17] also worked with same 2D-3D tin halide perovskite and got much improved parameters as VOC 0.52 volt, JSC 20.00 mA/cm2, FF 71.60% and PCE 7.4%. Ke Chen et al. [18] utilized ITO/PEDOT: PSS/LDP/FASnI3/C60/BCP/Cu architecture and obtained VOC 0.45 volt, JSC 24.87 mA/cm2, FF 63% and PCE 7.05%. At interfaces, carrier recombination happens so two interface defects are inserted in simulation architecture: HTM / FASnI3 and FASnI3 / ETM. Thermal velocity of both charge carriers is same i.e. 10 7 cm/sec. Neutral defects and Gaussian energetic distribution are there in both FASnI3 perovskite and in two interfaces with defect density 1017 cm-3. In addition tunnelling to interface traps is prohibited in this photovoltaic simulation work.

3. RESULTS AND DISCUSSION In this simulation, we worked on how some fundamental parameters of photovoltaic like defect density, operating temperature, doping concentration, thickness and band gap influence the performance of device. Simulation results obtained by simulation tool are nearly identical to experimental work (TABLE 3).

𝑅𝑆𝑅𝐻 =

𝑝.𝑛−𝑛𝑖2

𝜏𝑝(𝑛+𝑛𝑖 )+𝜏𝑛(𝑝+𝑛𝑖 )

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3.1. Defect Density (Nt): Quality of absorber layer affects the device performance. If film quality is poor, defect density of absorber layer becomes large and recombination process in space charge region increases [14]. At this recombination area energy loss happens and heat is generated. How defect density affects the photovoltaic performance can be described by Shockley-Read-Hall (SRH) recombination model: (6)

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where RSRH is the rate of recombination, n and p are concentration of electrons and holes respectively and τn and τp are life time of these charge carriers. By varying defect density from 10 15 to 1019 cm-3, modification of parameters is reviewed. Below 1015 cm-3 there is no effect of defect density on PCE but above this value all parameters are severely affected. By analysing fig. 3, at 1015 cm-3, VOC 0.97 V, JSC 25.95 mA/cm2, FF 80.85%, PCE 9.01% and at 10 19 cm-3, VOC 0.61 V, JSC 20.85 mA/cm2, FF 70.54%, PCE 5.87% parameters obtained. So lower the defect density higher will be the device performance. Nt 10 15 cm-3 can be termed as optimized defect density because at this value, all photovoltaic parameters have their maximum magnitude [19-20]. As defect density increases performance decreases, the reason behind this is here defects behave like recombination sites and ultimately decreases the life span of electrons and holes. In tin based perovskites the diffusion length of both charge carriers i.e. electrons and holes is almost same that is why photovoltaic performance is appreciable.

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3.2. Doping Concentration (NA): Tin based perovskites suffer from unfavourable self-doping process as unstable sn2+ oxidation state is oxidized at room temperature into more stable sn4+ oxidation state [20]. Doping concentration in perovskite absorber layer can vary form 10 14/cm3 to 1017/cm3 and how parameters are affected by this, are observed. Optimized VOC, JSC, FF and PCE occurred at 1E17 as 0.71 V, 20.42mA/cm2, 71.27% and 8.35% respectively as demonstrated in fig. 4. As doping concentration in absorber layer increases electric field inside the perovskite layer also enhances which results in increase in segregation of excitons and this results in increase in photovoltaic performance. But the main spoiler is as doping concentrating increases, according to Hui-Jing Du et al. [5] there is also increment in unwanted recombination process which outcomes in reduction of open circuit voltage VOC if we go towards higher concentrations i.e. beyond 1017 cm-3. So only at reasonable NA, short circuit current density and open circuit voltage can amplify [20].

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3.3. Operating Temperature (T): Photovoltaic performance of device is deeply affected by working temperature. Working temperature in this simulation work is set to be 300K. To observe how operating temperature affects the solar cell parameters, it is varied from 300K to 450K. As temperature increases the carrier concentration and their mobility get seriously influenced as obstruction in path modifies with temperature and this results in poor performance and PCE [21-22]. In this simulation work operating temperature is set to be 300K and irradiance of 1000W/m2 with AM 1.5G is applied. In fig. 5(a) variation in solar cell parameters according to working temperature are depicted. At 300K simulation outcomes in VOC 0.58 V, JSC 20.42 mA/cm2, FF 68.18%, PCE 8.01%. As temperature rises towards 450K from 300K the simulation results in VOC 0.37 volt, JSC 20.31 mA/cm2, FF 60.99%, PCE 4.43%. This happens because with the increase in temperature stress and strain also increases that causes the distortion and disorderness in the absorber layer. Pin-holes take this situation to new worsen level and uninvited recombination happens that cost in enhancement of resistance and ultimately it minifies the device performance and PCE. So best photovoltaic performance we got at 300K [23-24]. 3.4. Thickness: As thickness of perovskite absorber layer decreases the rate of light absorption also decreases and so does the overall efficiency of photovoltaic device. Charge carriers approach towards the ETM or HTM i.e. collecting layer through perovskite layer, if thickness is more then there is probability that they may not attain collecting layer because they have to cross it to do so. Number of charge carriers in perovskite absorber layer magnify as thickness exceeds so does the PCE and short circuit current density [25]. In this simulation at 0.56µm thickness, photovoltaic parameters are optimized and those are PCE 8.99%, FF 61.95%, JSC 25.70 mA/cm2 and VOC 0.56 V described in fig. 5(b). To inspect how thickness affects the solar cell parameters we vary thickness from 0.1µm to 1µm. Short circuit current density increases because thick perovskite absorber layer will now absorb more photons so generation of excitons will also be more, but with thick absorber layer unwanted recombination will increase because large diffusion length so after a moment PCE decreases with thickness [26]. If thickness of absorber layer is greater than the diffusion length of charge carriers then there is possibility that they may suffer recombination even before

arriving at metal electrodes. Unfavourable recombination process can only be avoided by lowering the absorber layer thickness. In this work optimized absorber layer thickness is 0.56µm [27].

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3.5. Band Gap: For best photovoltaic performance band gap of absorber layer should be 1.34eV that is known as Shockley–Queisser limit. Exquisite band gap matching of hole transporting material, absorber layer and electron transporting material allows us to fulfil desirable PCE. Band gap of lead free perovskites can be tuned between 1.3eV to 2.15eV. By analysing simulation results it is observed that as band gap increases except VOC, all remaining parameter decreases. Increase in band gap of absorption layer causes lowering of absorption of light photons so short circuit current density decreases [28]. As band gap increases open circuit voltage also increases and it happens because after generation of charge carriers segregation of excitons occurs which improves the VOC. Open circuit voltage is a function of band gap so it enhances VOC but because of imbalance between hole transporting layer and perovskite layer reduction in fill factor is observed. So overall by exploring results of simulation one can deduce that as band gap increases PCE of photovoltaic device decreases [29]. Best result is obtained at 1.33eV i.e. VOC 0.62 V, JSC 20.55 mA/cm2, FF 77.97% and PCE 9.99% shown in fig. 5(c). PCE of tin based photovoltaic devices still very low as compare to lead based devices because of poor film quality of perovskite absorber layer and poor step coverage on NiO hole transporting material [30]. This simulation shows that by reducing the total defect density in perovskite layer and by enhancing the stability of Sn 2+ oxidization state PCE and performance of device can be improved. By accounting all optimized parameters high power conversion efficiency and high performance of photovoltaic device can be achieved with FASnI 3 based structure. Optimized parameters are shown in table 2.

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3.6. JV and Quantum Efficiency Curve: Analysis of short circuit current density and voltage relation is the most vital component in solar cell simulation and modelling. By taking all the parameters into consideration current density against voltage curve is plotted for FASnI3 based perovskite absorber. In fig. 6, J-V and quantum efficiency (QE) curves are shown for both experimental and simulation work. Simulation results obtained by device simulation software are nearly identical to experimental work performed by Weiqiang Liao et al. [14] and Konstantakou et al. [19].

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Due to narrow band gap of FASnI3, absorption shifts to 850 nm for tin based perovskite solar cell and this quantum efficiency curve encloses the overall visible spectrum (400-750 nm) and gives broad absorption maximum up to 80%. Even near infrared light photons can also be absorbed by absorber layer in photovoltaic device [31-32].

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In best of our knowledge, for FASnI3, in reported literature maximum photovoltaic parameters achieved, are PCE 7.40% [17], Voc 0.52 V [17], Jsc 25.71 mA/cm2 [15] and FF 74% [16] so in this simulation analysis we obtained much improved results especially high output voltage (0.9672 V) and PCE (9.99%). 4. CONCLUSION

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FASnI3 based inverted perovskite solar cell is simulated by SCAPS-1D with different cell parameters. Tin based perovskite solar cells consist advisable characteristic like long carrier diffusion length, wide absorption spectrum, high carrier mobility and low temperature processing. Simulations results show that with inverted structure FASnI 3 perovskite solar cell can obtain maximum PCE up to 9.99%. Solar cell parameters alter as the operating temperature is varied from 300K to 450K and maximum PCE found at 300K. Thickness of perovskite absorber layer is varied from 0.1µm to 1µm and maximum PCE 8.97% obtained at 0.5µm. By lowering defects in absorber layer and by reducing self-doping process photovoltaic function can be reformed. By analyzing simulation results one can tell about how material properties affect the photovoltaic performance of device. This research work can give a new direction to design high performance perovskite solar cells. ACKNOWLEDGE

Author would like to thank Professor M.Burgelman for developing SCAPS simulation tool and allowing us to use it. Author also would like to acknowledge electrical engineering department, Indian institute of technology, Patna for providing support and encouragement for this work. REFERENCES

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Figure captions

(a)

(b)

Energy Band Diagram

1

-1 FTO

NiO

CuI

FASnI3

C60

BCP

Ec

-2

0

Energy (eV)

Energy(eV)

Conduction Band Valence Band

Au

-3 -4 -5

-1 -2 Ev

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-3 -6

0.0

-7

Layes of Device

0.1 0.2 0.3 0.4 0.5 0.6 length along the device (m)

Vacuum level (0 eV)

Light

EA

IP

Energy (eV)

WF

e-

LUMO

e-

1.41 eV

e-

LUMO

U

HOMO

Fermi energy level

Eg

h+ +

NiO (HTM)

C60 (ETM)

(c)

Au electrode

A

Built in electrical field

HOMO

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FTO

N

h+

D

Fig 1. (a) Energy diagram of perovskite solar cells in traditional structure (HTM/ Perovskite/ ETM), (b) Conduction and valence band energy levels for perovskite structure, and (c) Energy band diagram of NiO/Perovskite/C60 heterojunction solar cell under illumination exhibiting carriers being generated by incoming radiation, quantities expected for device modeling like work function (WF), ionization potential (IP), band gap (Eg), electron affinity (EA).

Absorber layer

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Hole transporting layer

C60

30 nm

FASnI3

350 nm

NiO

350 nm

FTO/ Glass

Transparent conducting oxide

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60 nm

Au

EP

Buffer layer

TE

Metal electrode

Light Fig 2. Schematic architecture of simulated PSC mode

500 nm

Average solar cell thickness 1.29 µm

82 80

9.5 FF PCE 9.0

1.00 0.95

Voc 26 Jsc

8.5

0.90

25

8.0

0.85

7.0

72

6.5

Voc (Volt)

7.5

74

24

0.80 23

0.75 0.70

22

0.65

21

SC RI PT

6.0

70

0.60 5.5

0.0

2.0x10

18

4.0x10

18

6.0x10

18

8.0x10

18

1.0x10

Jsc (mA/cm2)

76

PCE (%)

FF (%)

78

20

19

0.0

2.0x10

18

4.0x10

18

6.0x10

18

8.0x10

18

1.0x10

19

Total defect density (1/cm3)

Total defect density (1/cm3)

Fig 3. Variation in solar parameters with total defect density of photovoltaic device

71

19

70

18

0.64 0.62

17

0.60

8.3 8.2 8.1 8.0

68

7.9

67

16

0.58

7.8

66

M

0.56 0.0

69

8.4

PCE (%)

0.66

FF PCE

U

20

Jsc (mA/cm2)

Voc (volt)

0.68

72

N

0.70

21

FF (%)

Voc Jsc

A

0.72

7.7

15

2.0x10

16

16

16

4.0x10 6.0x10 8.0x10 Doping Concentration (1/cm3)

16

1.0x10

17

0.0

2.0x10

16

4.0x10

16

6.0x10

16

8.0x10

16

1.0x10

17

Doping Concentration (1/cm3)

350

420

EP

64

CC

20.30

Jsc

A

Jsc (mA/cm2)

62

Voc (volt)

Voc (volt)

0.5

(a) 280

350

Temperature (K)

420

PCE (%)

7

60

PCE

FF

80 60

40 20.60

55 30

Jsc

20.55

25

Jsc 20

20.50 20.45

Voc

0.575 0.570

0.560 0.0

2.0

0

65

0.565

1.5

5

FF

15 0.580

Voc

0.6

0.4

FF (%)

66

8

6 70

FF

Jsc (mA/cm2)

FF (%)

4 68

1.0 10

FF(%)

5

1.2

PCE

20.40 0.62

Voc (volt)

6

20.35

0.8

9

PCE (%)

7

20.40

0.4

TE

PCE (%)

8

60 20.45

0.0

PCE

Jsc (mA/cm2)

280 9

D

Fig 4. Variation in solar parameters with doping concentration of absorber layer

(b)

0.60 0.56 0.54

0.4

0.8

Thickness (m)

1.2

Voc

0.58

1.0

(c) 1.5

Band Gap (eV)

Fig 5. Variation in solar parameters of photovoltaic device with (a) working temperature, (b) thickness, and (c) band gap

2.0

100

Simulation Experimental

-5

-10

-15

-20

-25 0.0

75

Simulation Experimental

50

25

0 0.1

0.2

0.3

0.4

0.5

400

Output Voltage (Voc)

SC RI PT

Quantum Efficiency (%)

Current Density (Jsc)

0

500

600

700

800

900

Wavelength (nm)

A

CC

EP

TE

D

M

A

N

U

Fig 6. J-V and Quantum efficiency-wavelength curves obtained from both simulation and experimental work which are almost identical to each other

Table TABLE 1. SIMULATION PARAMETERS FOR FASNI3 BASED PSC NiO

FASnI3

C60

Thickness (nm)

500

350

350

30

Band Gap Eg (eV)

3.50

3.80

1.41

1.9

Electron Affinity (eV)

4.00

1.46

4.47

2.65

Dielectric Permittivity

9.00

11.75

8

4.5

CB Effective Density of States cm-3

2.2E+18

2.2E+20

6.76E+17

1.44E+21

VB Effective Density of States cm-3

1.8E+19

1.8E+19

6.76E+17

1.44E+21

Mobility (µe) cm2/vs

20

2.8

1.6

1.0E-2

Mobility (µh ) cm2/vs

10

2.8

1.6

1.0E-5

-

1.0E+18

1.0E+19

2E14

2.0E+19

-

-

-

Total Defect Densitycm-3

1015

1015

1013

1015

Electron Thermal Velocity cm/s

1E7

1E7

1E7

1E7

Hole Thermal Velocity cm/s

1E7

1E7

1E7

Shallow Uniform Acceptor Density cm-3

1E7

N

Shallow Uniform Donor Density cm-3

SC RI PT

FTO

U

Parameters

M

A

TABLE 2. OPTIMIZED PARAMETERS OBTAINED FOR BEST PERFORMANCE OF PHOTOVOLTAIC DEVICE Optimized parameter

Total defect density(Nt) cm

-3

FASnI3

HTM

1E15

1E17

1E15

2E14

1E17

1E18

D

Doping concentration (Na) cm-3

ETM

30

560

350

Band Gap

1.9

1.33

3.8

TE

Thickness (nm)

A

CC

EP

TABLE 3. SOLAR CELL PERAMETERS SHOWING SUPERIOR AGREEMENT WITH EXPERIMENTAL WORK

VOC (volt)

JSC (mA/cm2)

FF (%)

PCE (%)

Reference

0.9672 0.4700 0.4650 0.3800 0.4700 0.5200 0.4500

25.9504 22.4500 22.0700 25.7100 20.0700 20.0000 24.8700

80.85 67.80 60.67 49.05 74.00 71.60 63.00

9.99 7.09 6.22 4.81 6.98 7.40 7.05

This work [13] [14] [15]

[16] [17] [18]