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Lead-free perovskite solar cell byUsing SCAPS-1D: Design and simulation

Article in Materials Today Proceedings · May 2022

DOI: 10.1016/j.matpr.2022.04.832

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 Materials Today: Proceedings xxx (xxxx) xxx

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Lead-free perovskite solar cell byUsing SCAPS-1D: Design and simulation

Manas Tripathi a, Vipul Vaibhav Mishra a, Brajendra S. Sengar b, A.V. Ullas a,⇑
a
Centre for Advanced Studies, Dr. A.P.J. Abdul Kalam Technical University Lucknow, Uttar Pradesh 226031, India
b
Department of Electronics and Communication Engineering, National Institute of Technology, Srinagar, India

a r t i c l e i n f o a b s t r a c t

Article history: The efficiency of photovoltaic systems of perovskite materials based on organic–inorganic halide has
Available online xxxx increased and they are nearing commercialization. Lead-free perovskite materials have recently attracted
the interest of researchers and the scientific community due to the toxicity issue and harmful lead-based
Keywords: perovskite materials. Tin, like lead (Pb) is a group 14 metals; hence, it is the most likely substitute. We use
SCAPS-1D SCAPS-1D numerical simulation to optimize the device efficiency of a lead-free n-i-p based planar het-
CH3NH3SnI3 rostructure perovskite solar cell composed of intrinsic-CH3NH3SnI3 methyl ammonium tin iodide
Lead-free
(MASnI3) as an i- and p-layer Spiro-OMeTAD with SnO2 for the n layer. Conclusions show that the absor-
Perovskite
ber layer has a thickness of 600 nm, which is required for optimal cell performance and efficiency. The
thickness and defect density of this absorber layer was taken into account, absorption coefficient is inver-
sely proportional to defect density. The performance of device worsens when the defect density of absor-
ber layer increases. The thickness and defect density of absorber layer was carefully tuned to get
maximum solar cell performance and we observed an efficiency of 22.21 %, current density (JSC) of
33.8636 mA/cm2, VOC of 0.989 V and FF of 66.33 % at 600 nm thickness of absorber layer.
Ó 2022 Elsevier Ltd. All rights reserved.
Selection and peer-review under responsibility of the scientific committee of the International Confer-
ence on Materials, Processing & Characterization.

1. INTRODUCTION mitigate the silicon-based market, the use of new generation mate-
rials and devices such as dye-sensitized solar cells (DSSCs), thin-
Energy demand is expected to soar in the future. The majority of film cadmium telluride (CdTe), and thin-film copper indium gal-
today’s energy comes from fossil fuels, which will be depleted in lium selenide (CIGS) based solar cells has elevated, but some of
the near future and it pollute the environment due to carbon foot- them contain expensive and toxic elements. Perovskite solar cells
print. So the most difficult task is to build a renewable energy have caught researchers’ attention over the years owing to their
source since renewable energy is now in high demand. Industrial- inexpensive processing costs, solution processing, and excellent
ization and population growth are driving up the cost of energy. light properties, and also an efficiency of up to 25.2 %[3]With rapid
Solar energy is an emerging technology for this purpose as well evolution toward 25 % power conversion efficiency (PCE) the per-
as for future prospect also because it is clean and has no negative ovskite solar cell (PSC) has emerged as one of the most promising
environmental impact. photovoltaic technologies, it could replace the conventional silicon
There is a need for long-term energy solutions on such a global solar cell. The perovskite solar cells (PSCs) continue to catch the
scale [1,2]. Silicon-based solar cells are extremely expensive and attention of the scientific community about photovoltaic world
only have 15–25 % efficiency, but they have dominated the solar [1,4]. The greatly tunable perovskite bandgap facilitates light
business for many years, with a 94% market share. As a result, a absorption from near-infrared to visible wavelengths via simple
comprehensive search for alternative solar materials has become structural element substitution. PSCs still have fundamental issues
the need. Thin-film technologies have revolutionized the solar cell to tackle, such as the toxicity of hybrid lead halide perovskites,
market during the 2000 s, enhancing solar cell efficiency by up to hysteresis, and structural instability when exposed to moisture,
21% and making solar cells lighter, thinner, and more robust. To light, and heat. However, the commercial viability of their develop-
ment has been studied [5] in recent years; the power conversion
efficiency of perovskite solar cells has improved significantly.
⇑ Corresponding author. Although there are various perovskite materials, CH3NH3PbI3(-
E-mail address: avullas@cas.res.in (A.V. Ullas).

https://doi.org/10.1016/j.matpr.2022.04.832
2214-7853/Ó 2022 Elsevier Ltd. All rights reserved.
Selection and peer-review under responsibility of the scientific committee of the International Conference on Materials, Processing & Characterization.

Please cite this article as: M. Tripathi, V. Vaibhav Mishra, B.S. Sengar et al., Lead-free perovskite solar cell byUsing SCAPS-1D: Design and simulation, Mate-
rials Today: Proceedings, https://doi.org/10.1016/j.matpr.2022.04.832
M. Tripathi, V. Vaibhav Mishra, B.S. Sengar et al. Materials Today: Proceedings xxx (xxxx) xxx

MAPbI3) is most commonly employed as an active layer in solar 3. ANALYSIS OF NUMERICAL SIMULATION AND METHODOLOGY USING SCAPS-1D
cells. Because it includes lead (Pb), which is extremely dangerous
to humans and degrades rapidly when exposed to environment, a Under the standard AM 1.5G solar spectrum irradiance, the
suitable replacement of CH3NH3PbI3 is being explored all over the research methodology of simulation is being made to numerically
world. To solve this difficulty, lead (Pb) in the perovskite layer model of perovskite solar cell by using one-dimensional solar cell
could be substituted with tin (Sn), the bandgap of the MASnI3- capacitance simulator SCAPS-1D (version 3.3.07) software for af-
based perovskite layer is about 1.3 eV, which is significantly lower fecting the spectral response of solar energy with different homo-
than the MAPbI3-based PSC (1.6 eV) [20]. It’s also safe to assume junction and heterojunction architecture [4,8].
that in the perovskite layer, MASnI03 s lower bandgap effectively To describe the physics of the photovoltaic structure and track-
absorbs photons with a considerably wider visible range than ing behavior of the photovoltaic that are required for charge carrier
MAPbI3[6,7]. So we discuss here solar cell analysis of photovoltaic transport, the software is often numerically based on solving con-
devices using materials methylammonium tin triiodide (CH3NH3- tinuity, Poisson’s, and semi-conductor equations.
SnI3) as the photoactive material, which is fully lead-free[2]. Tun- In computing the electrostatic potential within the device a
able bandgap, lesser excitation binding energy, high opt electrical continuity equation in the position domain is used to depict the
properties, longer carrier diffusion distance, and excellent perfor- movement of photo generated charge carriers within the solar cell.
mance almost equal to silicon-based solar cells are all features of Poisson’s equation, Recombination of electron-hole[9].
hybrid organic–inorganic metal halide perovskite solar cells. For a semiconductor, Poisson’s equation is given:
Under simulation work in this paper the device performance
under AM1.5G light is simulated using a 1D-solar cell capacitance r2 w ¼ qeðn  p þ NA  ND Þ ð1Þ
simulator (SCAPS, ver.3.3.07).The thickness and doping levels of Where NA is acceptor doping concentration and ND is the donor
several layers, such as the electron transport layer, perovskite doping concentration and w is the electrostatic potential.
absorber layer, and hole transport layer, were tuned, and their The continuity equation is shown below for a semiconductor.
results being taken into account for further performance
optimization. @n
r:Jn  q ¼ þq R ð2Þ
@t

2. @p
DEVICE MODELLING AND SIMULATION r:Jp þ q ¼ q R ð3Þ
@t
2.1. Device structures Where Jnis represented by current density for electrons conduct
to flow of current to transfer charge the charge carrier in semicon-
Fig. 1 In such structure, MASnI3 is absorption layer is also called ductor due to two mainly effect known as drift and diffusion cur-
active layer and this one is inserted between both the ETL(Electron rent, where drift current due to electric field and diffusion
Transport Layer) and the HTL(Hole Transport Layer), as an interfa- current cause of charge carrier concentration gradient [10].
cial layer. To optimize the device performance, the thickness of the Then from continuity equation--.
ETM (Electron Transport Material), HTM (HoleTransport Material),
and absorber layers is tuned over a wide range. As a result, the J n ¼ qnln E þ qDn rn ð4Þ
device simulation is done in n-i-p mode of a structure of perovskite
solar cell based on MASnI3 with planar heterojunction FTO/TiO2/ rJp ¼ qplp E  qDp rp ð5Þ
MASnI3/HTL/Au. Where light incidents through fluorine-doped
Where Dp and Dn denotes for the hole diffusion coefficient and
tin oxide FTO with a work function of4.4 eV selected as a TCO
the electron diffusion coefficient respectively.
(Transparent Conductive Oxides)and considered to have a thick-
SCAPS 1D software package interfaces, which consolidate all
ness of 500 nmand gold (Au) as the metal back contact.[10] Under
of the parameters in TABLE 1 and are used during simulation,
AM 1.5 G 1 Sun spectra, the simulation is performed using the solar
according to the literature.
cell capacitance simulator (SCAPS 1-D).
The parameters of interface layers are systematically deter-
So many properties that have been entered during the simula-
mined from simulations of research work.
tion include the various layers of thicknesses, elec-
As a result, this verifies that the device simulation’s output is
tron and hole mobility, electron affinity, thermal velocities,
appropriate, so furthermore, the input parameters are similar to
band gap, doping concentration, dielectric permittivity, conduc-
those of a real device.
tion band (CB), and valance band (VB), Effective densities of states.
And it shows a list of values that were taken into account during
the simulation process in order to achieve optimal result by
switching different values. So researching over how factors affect
the device’s functioning.

4. RESULTS AND DISCUSSION

Based on the analysis of simulated model we observed voltage

vs current density curve for different thickness of absorber layer
which is shown in Fig. 2. We observed that after 600 nm thickness
of absorber layer the current density increases very slightly for
800 nm and 1000 nm thick absorber layer. So, we consider
600 nm optimize thickness for our PV Solar cell.
The thickness of active layer of PSC Structure plays a significant
role and influence to the performance of solar cell device through
numerical simulations, Jsc, Voc, FF, and PCE are often effected by
Fig. 1. MASnI3-based multilayer solar cell configuration. varying the absorber layer thickness from 100 to 1000 nm, while
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M. Tripathi, V. Vaibhav Mishra, B.S. Sengar et al. Materials Today: Proceedings xxx (xxxx) xxx

Table 1
Material Properties Used In Simulation.

Parameters FTO (TCO) SnO2 (ETL) CH3NH3SnI3 (absorber) Spiro-OMeTAD (HTL)

Thickness (nm) 500 50 Varied 200
Band gap (eV) 3.5 3.2 1.3 2.88
Electron affinity (eV) 4 4 4.17 2.05
Dielectric permittivity 9 9 6.5 3
CB effective density of states (1/cm3) 2.20E + 18 1.00E + 19 1.00E + 18 2.20E + 18
VB effective density of states (1/cm3) 1.80E + 19 1.00E + 19 1.00E + 19 1.80E + 19
electron thermal velocity (cm/s) 1.00E + 07 1.00E + 07 1.00E + 07 1.00E + 07
hole thermal velocity (cm/s) 1.00E + 07 1.00E + 07 1.00E + 07 1.00E + 07
Electron mobility (cm2 /V. s) 2.00E + 01 2.00E + 01 1.60E + 00 2.00E-04
Hole mobility (cm2 /V. s) 1.00E + 01 1.00E + 01 1.60E + 00 2.00E-04
shallow uniform donor density ND (1/cm3) 2.00E + 19 1.00E + 19 0.00E + 00 0.00E + 00
Shallow uniform acceptor density NA (1/cm3) 1.00E + 15 0.00E + 00 3.200E + 13 2.00E + 19
Defect density Nt (1/cm3) 1.00E + 13 1.00E + 16 1.00E + 14 1.00E + 15

as a result of the increased recombination rate of charge carriers,

resulting in a decrease in Voc [1].
Also, as mentioned above, the JSC and PCE (Power conversion
efficiency) immediately improve as the thickness of the absorber
layer increases due to increased exciton generation. Conversely,
increased thickness means excessive resistance (while also higher
defects and more recombination rates), leading to a fall in relevant
values [10].The efficiency falls as the thickness isreduced.
So, we can say that relatively thicker absorbing layer for per-
ovskite may trap higher photons, resulting in many excitons being
generated. So, we can say in other words that high absorption layer
thickness, on the other hand, may lead to a rise in the recombina-
tion rate and its diffusion length, making the power conversion
efficiency even deteriorate. Based on the foregoing results,
600 nm is the appropriate absorption layer thickness.

4.2. Impact on varying the defect density (Nt)

Influence of the defect density (Nt) of perovskite to the perfor-

Fig. 2. Voltage Vs Current DensityJsc at different thickness of absorber layer. mance of battery has been investigated using the composite model
equation by Shockley–read–Hall (SRH). The modeled simulated
defect has a very neutral Gaussian distribution, with the mean
other parameters remains unchanged, so the solar cell capacitance energy range of 0.6 eV, so that is the middle of the band gap. This
simulator is being used for simulation under the AM 1.5 G 1 Sun is a very common misinterpretation [8].
spectrum (SCAPS 1-D). The material properties used in simulation
are given in TABLE 1. p:n  n2i
RSRH ¼
spðn þ niÞ þ snðp þ niÞ
4.1. Impact on Varying the thickness of absorber layers Where the equation of SRH denotes the recombination rate, p &
n are just the concentrations for holes and electrons respectively
Effect of absorber (active) layer thickness on efficiency, fill fac- and sp, sndenote the period of life of the charge carriers [8].
tor, Jsc, and Voc is shown in this research. The absorber layer (ac- Because Shockley–read–Hall (SRH) recombination is one the
tive layer) thickness ranged from 200 nm up to 1000 nm. So that most common kind of the recombination inperovskite solar cells,
the variation with respectto device parameters to thickness of a SRH recombination model is being used to quantify of diffu-
absorber layer are shown in Fig. 3 (a).The diffusion length must sion length [4].
be large as compared to cell thickness. Diffusion length of minority Here, the defect density (Nt) value which is optimal for the
charge carrier usually very short due to existence of defects and the device setup is 1014 cm-3of FTO/TiO2/MASnI3/Spiro-OMeTAD/Au.
dominant charge separation is therefore drift, driven by electro- Fig. 3 (b) shows how the device’s performance parameters fluctu-
static field of the junction which extends to whole thickness of ate when the value of defect density (Nt) of the active layer (ab-
the cell. sorber layer) increases.
Because of the increased recombination rate of free charge car- As a result, the defect density (Nt) of the solar cells is essential
riers in the thicker absorber active layer, the device’s VOC and FF for reducing it to an appropriate value in improving the perovskite
values drop dramatically as thickness of its perovskite absorber device’s efficiency. One may eliminate the defect density (Nt) in
(active layer) layer increases [1]. It is because there are even more the absorber material all across the simulation process, but even
photons absorbed as the absorber layer thickness increases, but the this number of defects needs to be applied to make a reasonable
rate of recombination increases as well [4]. Increased series resis- and efficient perovskite device. The solar cell characteristics vary
tance may be linked to the decreasing value of FF in respect to from 1014 cm3 to 1018 cm3 depending on the defect density
absorber thickness [8]. In other words, exciton are formed as a (Nt) [1,11]. As given in TABLE 2 whenever the active layer (ab-
result of photon absorption and are unable to pass the barrier sorber layer) does have a high defect density value, the perfor-
potential (depletion layer). The reverse saturation current is higher mance of photovoltaic solar cell falls significantly because of
3
M. Tripathi, V. Vaibhav Mishra, B.S. Sengar et al. Materials Today: Proceedings xxx (xxxx) xxx

Fig. 3. Effect of (a) Thickness and (b) defect density (Nt)ofthe perovskite active layeron performance of Voc, FF,Jsc and PCE.

Table 2
Voc, Jsc, FF, Efficiency at varying defect density.

Defect density Nt(cm3) Voc (V) Jsc (mA/cm2) FF (%) Efficiency (%)
1.00E + 14 0.989 33.863596 66.33 22.21
1.00E + 15 0.8817 33.643578 54.21 16.08
1.00E + 16 0.7984 31.550742 37.22 9.38
1.00E + 17 0.7525 17.951358 17.14 2.32
1.00E + 18 0.7183 1.8157 11.13 0.15

increased recombination rate, the charge carrier life time is 5. CONCLUSIONS

reduced, resulting in poor device performance solar cell [1].
The performance tuning and designing of a planar hetero junc- Lead (Pb) free Methyl Ammonium Tin Iodide based perovskite
tion of such a new lead-free perovskite CH3NH3SnI3 solar cell as a solar cells (MASnI3) have been designed and simulated. We tried
light generator well with architecture FTO/TiO2/CH3NH3SnI3/ to optimize the thickness and defect density of Methyl Ammonium
Spiro-OMeTAD / Au have been analyzed and examined based on Tin Iodide using SCAPS-1D. We have simulated the PV solar cell
photovoltaic solar cell performance with various parameters have model using the architecture FTO/TiO2/CH3NH3SnI3/Spiro-
been intended and numerically simulated by using one- OMeTAD/Au for different thicknesses and defect density. The solar
dimensional solar cell capacitance simulator version 3.3.07. cell device has maximum power conversion efficiency of 22.21%
Its thickness of absorber layer does indeed have a major impact with 600 nm thickness of absorber layer (active layer). Also, we
on the performance of tin halide oriented perovskite solar cells, observed that the current density (JSC) is 33.8636 mA/cm2, the
and thus the result indicate that many considerations, along with VOC is 0.989 V and the FF is 66.33 % at a 600 nm thick absorber
the thickness and defect density of such a absorber layer, and even layer.
the thickness value, could be significantly changed to enhance the
efficiency of MASnI3 based perovskite solar cells with the a drop or
rise from this modeling’s optimal value, the highest efficiency CRediT authorship contribution statement
again for solar cell design FTO/TiO2/CH3NH3SnI3/ Spiro-OMeTAD/
Au with such a PCE of 22.21 %, FF of 66.33 %, JSC of 33.8636 mA/ Manas Tripathi: Methodology, Software, Data curation, Writing
cm2 and a VOC of 0.989 V can be obtained with determined that – original draft. Vipul Vaibhav Mishra: Validation, Formal analysis,
a relatively thin absorber layer with an ideal thickness of 600 nm Investigation. Brajendra S. Sengar: Supervision. A.V. Ullas: Writ-
is being used. ing – review & editing.

4
M. Tripathi, V. Vaibhav Mishra, B.S. Sengar et al. Materials Today: Proceedings xxx (xxxx) xxx

Declaration of Competing Interest References

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