Comprehensive Study and Photovoltaic

Performance Analysis of Eco-friendly

Perovskite Solar Cell
2021 25th International Symposium on VLSI Design and Test (VDAT) | 978-1-6654-1992-5/21/$31.00 ©2021 IEEE | DOI: 10.1109/VDAT53777.2021.9601057

Shubham1, Chetan Pathak1, and Saurabh Kumar Pandey2

1
Department of Electronics and Communication, RustamJi Institute of Technology (RJIT),
Gwalior 475005, India
2
Sensors and Optoelectronics Research Group (SORG), Department of Electrical Engineering,
Indian Institute of Technology Patna, Bihta 801106, India

Abstract— In this study, we have investigated a non-toxic, and a homologous element; thus is a potential candidate to
lead-free perovskite solar cell that follows a planer organic- replace Pb in MAPbI3.
inorganic hybrid architecture and realized using device
simulation software. We have discussed about the influence of MAGeI3 has many desirable and properties similar to
carrier lifetime and absorber doping density in the perovskite MAPbI3, like tunable bandgap, good optical absorption, and
absorber layer on the solar cell's performance. Moreover, a study
regarding the influence of carrier’s mobility in the perovskite great carrier conducting behavior[6][7][8]. As per author’s
layer on performance is also shown. Simulation results show an knowledge, only two experimental work has been reported
improved short circuit current density (Jsc) of 24.64mA/cm2, with MAGeI3 in which they obtained an efficiency of 0.2% [9]
open-circuit voltage (Voc) of 0.89V, fill-factor (FF) of 62.75%, and 0.57% [10]. However, theoretically, PSC based on
power conversion efficiency (PCE) of 13.80% through MAGeI3 has shown efficiency of up to 23.58% by using
optimization. This work is expected to provide a route towards
the development of eco-friendly perovskite solar cells. CuSbS2 as HTM[11]. Despite the concerned efforts, still the
study on performance optimization of MAGeI3 is limited.
Index Terms— Carrier Lifetime, MAGeI3, Mobility, Non-toxic,
In this work, numerical simulation of an eco-friendly
Perovskite, Absorber Doping
perovskite solar cell is carried out using a TCAD device
I. INTRODUCTION simulation software. We have investigated the device
performance by varying the carrier’s lifetime and absorber
Perovskite solar cells (PSCs) are the newest among the third
doping concentration. This work is expected to motivate the
generation of solar cells [1]. From the incorporation of
researcher to find a suitable material for lead-free PSCs.
perovskite in a dye-sensitized solar cell (DSSC) as a light-
sensitizer in 2009 by professor T. Miyasaka’s group to the
organic-inorganic hybrid architecture, which is heavily
followed today, PSCs has increased their efficiency from 3.9% II. DEVICE STRUCTURE AND METHODOLOGY
in 2009 [2] to 25.5% in 2020 [3]. This proves the immense The proposed device follows an inverted planar p-i-n hybrid
potential in the PSC, which can provide low-cost energy in the organic-inorganic architecture. This inverted architecture has
future. Besides these enormous potentials of PSCs, the chief an added advantage of lower temperature processing,
hurdles toward commercialization are toxicity and stability. negligible J-V hysteresis effect and flexibility. Fig 1 (a)
The most common perovskite material used today in the labs shows the schematic of ITO/PEDOT:PSS/MAGeI3/PCBM/Au.
is Methylammonium Lead Iodide (MAPbI3), which degrades This structure is modeled and simulated under the AM1.5G
with exposure to air and moisture. After degradation of the illumination using a TCAD device simulation software which
material, the Lead (Pb) can leach from the panel to the solves the basic semiconductor differential equation like
surrounding and pose a threat to human life. A solution to this continuity equation, Poisson equation, and charge transport
problem is substituting the Pb with a non-toxic element. equations to predict the electrical behavior and thus helps to
Germanium (Ge) and Tin (Sn) are the best alternatives[4]. Sn- get an insight through device internal mechanism[12]. The
based PSC has proved its potential by achieving 7.78%[5] extracted energy band diagram by simulating the device
power conversion efficiency (PCE). In comparison to Sn, Ge- structure is also presented in Fig 1(b), which shows the
based PSCs are less explored. Ge is earth-abundant, non-toxic, favored extraction of the photogenerated charge carrier. The

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interface defect density of states (DOS) is also considered For the modeling of recombination phenomenon, which is
along with bulk defect DOS. At both ETL-perovskite and mainly responsible for efficiency losses, SRH and radiative
HTL-Perovskite, shallow defect DOS is kept at 1011 cm-2 eV-1, band to band recombination process were taken into account
and deep level defect DOS is kept at 108 cm-2 eV-1. Gaussian as they are the most dominating recombination mechanism in
distribution is considered for modelling the distribution of PSCs[23]. SRH Recombination rate is given by:
deep-level defect DOS. For modelling the defect distribution
of shallow level defects, exponentially decaying distribution is
considered. Both of these distribution are characterized by −
=
their peak and width[13]. The absorber thickness of 600nm −
+ + +
was taken for the simulation as many studies have shown that
optimal thickness for MAGeI3 based PSC is between 600- Here, p and n are the concentration of holes and electrons,
800nm[13], [14]. ITO and Au were taken as conductors with ni is the intrinsic carrier concentration, and are carrier
no resistance. lifetimes, ETRAP is the difference between intrinsic fermi
energy level, K and T are the Boltzmann constant and lattice
All the material properties and defect-related parameters as temperature, respectively. The Radiative recombination rate is,
taken from the available recent theoretical and experimental
literature studies [9][15][16][17][18][19][20][21][22] and are = " − #
presented in Table 1. B is the capture rate often known as the radiative band-to-band
recombination coefficient[24].
Table 1 Material Parameters for the simulation
A.M. 1.5
Material properties PEDOT:PSS MAGeI3 PCBM
ITO/Glass (anode) Eg (eV)
χ (eV)
1.6
3.4
1.9
3.98
2.2
3.91
μn (cm2V-1s-1) 0.00045 16.2 0.002
p-PEDOT:PSS (HTL) μh(cm2V-1s-1) 0.001 10.1 0.002
εr 3 10 3.9
Nc 1022 1016 2.5x1021
Nv 1022 1015 2.5x1021
i-MAGeI3(Absorber) Na (cm-3)
Nd (cm-3)
1019
0
1014
0
0
1019
Thickness 50nm 600nm 50nm
, (sec) 10-9 10-8 10-9
B (cm3 s-1) 1x10-13 8.1x10-11 1x10-13
n-PCBM (ETL) Peak Defect DOS at 1x1018 5x1018 1x1018
bandtails (cm-3 eV-1)
Au(cathode) Width of bandtails 50 63 50
(meV)
(a) Peak Defect DOS at 1015 1016 1015
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 Mid-gaps (cm-3 eV-1)
Width of mid-gap 90 100 90
1.5 Valence Band(eV) 1.5 states (meV)
Conduction Band(eV)
PEDOT:PSS

1.0 1.0

0.5 0.5 III. RESULTS AND DISCUSSION

ITO
Energy (eV)

0.0 0.0 The above-proposed model is simulated using the parameters

presented in Table 1, shows a good amount of short circuit
-0.5 MAGeI3 -0.5 current JSC = 24.49 mA/cm2 and open-circuit voltage of VOC =
PCBM

-1.0 -1.0 0.88 V, fill factor of FF = 54.81 %, and a power conversion

efficiency, PCE= 11.83 % which has also shown a good
Ag

-1.5 -1.5
agreement with some available literature[11][13][14][25]. We
-2.0 -2.0 have studied the effect on the performance of cell modules by
carrier lifetime, absorber doping concentration, and charge
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7
carrier’s mobility.
Distance (µm)
(b)
a) Effect of carrier lifetime on the performance
Figure 1 (a) Schematic of the proposed PSC (b) The Energy Band
Carrier lifetime varies significantly across the materials.
Diagram of the cell
Single crystals perovskites allow a carrier lifetime up to tens

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of microseconds[26], [27]. Inside a polycrystalline material, the doping level of 1014 cm-3 with PCE at 11.83%, and after
carrier lifetime varies greatly depending on the crystallinity, that, at 1015 cm-3, PCE reduced to 11.77%, and performance
intrinsic defects, and grain boundaries. Thus, in this section starts degrading with further increase in doping. Finally, at
effect of carrier lifetime on the cell’s performance is done by 1018 cm-3, it reduces to 0.55%. This happens because of the
varying both electron and hole lifetimes from 10-5 s to 10-10 s, decrease in the depletion layer, causes a decrease in carrier
and the result is presented in Fig 2. As seen from the figure, collection; thus, the current is reduced, which can be
the efficiency is almost constant at 11.83% until the carrier confirmed by the decrease in Jsc.
lifetime is 10-6 s. As the lifetime reaches 10-7 s, the efficiency
decreases to 11.75%, and after that, the performance decreases c) Effect of hole’s mobility in the absorber layer
drastically. Finally, at a lifetime of 10-10 s, efficiency reduces Mobility of charge carriers varies from polycrystalline thin
to the minimum of 2.70%. This happens because when carrier films to single crystals. In planer PSC usually, a thin film of
lifetime reduces, its chance of annihilation before reaching the the perovskite act as an absorber. The performance of the cell
electrodes increases which results in significant loss of charge depends on how efficiently the photogenerated charge carriers
carriers, resulting in a decrease in current Jsc, and the are transported through the cell. For which mobility plays a
vital role. Hence, here in this section, the mobility of holes in

1E-5 1E-6 1E-7 1E-8 1E-9 1E-10 1E10 1E11 1E12 1E13 1E14 1E15 1E16 1E17 1E18
15 15
PCE (%)

10

PCE(%)
10
5
5
0
0
70
50
FF (%)

FF (%)

40 60
30
50
20 0.89
0.88 0.88
Voc (V)

Voc (V)

0.87
0.87 0.86
0.85
0.86 0.84
30
Jsc (mA/cm2)

Jsc (mA/cm2)

25
20
20
10
15 0
1E-5 1E-6 1E-7 1E-8 1E-9 1E-10 1E10 1E11 1E12 1E13 1E14 1E15 1E16 1E17 1E18
Carrier Lifetime (sec) -3
Absorber Doping Concentration (cm )
Figure 2 Variation in performance parameters with respect to varying Figure 3 Variation in performance parameters with respect to varying
carrier lifetime absorber’s doping level

performance of the cell. the perovskite absorber layer is varied from 1 cm2/V-s to 40
cm2/V-s while keeping the mobility of electrons constant. Fig
b) Effect of absorber doping concentration 4 presents the influence of the mobility of holes on the
Doping plays a significant role in deciding the electrical performance parameters. As mobility varies, it can be seen
properties of semiconducting material. Doping in this layer is that the PCE is first increased at a rapid pace from 8.62% and
a critical factor that decides the performance of the cell. Too then began to saturates at higher mobility. At 40 cm2/V-s,
much doping in this layer reduces the depletion width; thus, it PCE attains a value of 13.22%. This is due to the fact that fast-
presents a tradeoff between doping and the depletion width, moving charges are less prone to recombination, and hence
and hence doping level plays an essential role in any solar cell. recombination rate is relatively lower at higher carrier
Here in this study, the doping level in the perovskite is varied mobility, which is confirmed by noticing a rapid increase in
from 1010 cm-3 to 1018 cm-3, and the results are presented in Fig Jsc also. It can also be seen that the Jsc began to saturate at
3. The result shows the performance is nearly the same up to

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higher mobility; this tells us that too much mobility has no 14.69 0.97 86.97 12.35 [14]
significant effect on the performance. 23.07 0.87 55.37 11.16 [25]

0 20 40 0 20 40
14
14
12
PCE (%)

PCE (%)
12 10
8
10 6
4
8
60 60
FF (%)

FF (%)
55 55
50 50
45 45
0.890 40
0.89

Voc (V)
Voc (V)

0.885 0.88
0.880 0.87
0.86
0.875
JSC (mA/cm2)
Jsc (mA/cm2)

24.5 25
24.0
20
23.5
15
23.0
0 20 40 0 20 40
Mobility of holes in absorber layer (cm2/V-s) Mobility of electron in Absorber Layer (cm2/V-s)
Figure 4 Variation in Performance parameters with respect to varying Figure 5 Variation in Performance parameters with respect to varying
mobility of holes in absorber layer Electron’s mobility in absorber layer

d) Effect of Electron’s mobility in the absorber layer IV. CONCLUSION

To summarize, we have analysed and evaluated the
An equal number of electrons and holes are generated upon
performance of an eco-friendly perovskite solar cell by
the incidence of sun rays on the solar cell. Hence the impact of
varying carrier lifetimes and absorber’s doping concentration.
mobility of both types of charge carriers must be considered.
In this, electron mobility is varied from 1 cm2/V-s to 40 The study shows that the carrier lifetime, carrier mobility, and
cm2/V-s while keeping mobility of holes constant at 40cm2/V- doping concentration in perovskite play a substantial role in
s, which was optimal value came from previous sub-section determining the cell's performance. It was found that the
simulation. Fig 5 presents the results, which show the carrier lifetime for both electron and hole should be greater
influence of electron mobility on the performance parameters. than 10-7 sec, and the absorber doping level should be less
At the first rapid increase in Jsc from 14.74 mA/cm2 and PCE than 1015 cm-3 for achieving high performance. It was also
from 5.52 %, it can be noticed. This is due to reduced shown that the carrier’s mobility up to 20 cm2/ V-s in the
recombination, and then saturation is also noticed at higher absorber layer is essential to enhance efficiency. Still, there is
mobility where PCE saturated at 13.80%, and Jsc saturated at much space for further optimization for these lead-free PSCs.
24.68 mA/cm2. This emphasizes that both charge carriers’ These results are expected to motivate the researchers
mobility makes a significant impact on the cell’s performance.
worldwide to infer MAGeI3 based solar cells for future choice
We have also presented the comparison of our investigated of material.
cell with various other available in the literature.
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