2019 International Conference on Electrical, Computer and Communication Engineering (ECCE), 7-9 February, 2019

Performance Analysis of Perovskite Solar Cells

with Different Structures
Partha Protim Mondal Md. Sakib Hasan Khan Md. Rejvi Kaysir
Department of EEE Department of EEE Department of EEE
Khulna University of Engineering & Khulna University of Engineering & Khulna University of Engineering &
Technology Technology Technology
Khulna, Bangladesh Khulna, Bangladesh Khulna, Bangladesh
parthaprotimeee@gmail.com kuet.sakib@gmail.com rejvi@eee.kuet.ac.bd

Md. Rafiqul Islam

Departmen of EEE
Khulna University of Engineering &
Technology
Khulna, Bangladesh
rafiq043@yahoo.com

Abstract—Perovskite solar cells (PSCs) have recently different layers (i.e., using different structures). There are
emerged as a promising candidate for photovoltaic technology mainly two basic structures of PSCs: p-i-n and n-i-p. Most of
because of their potential low cost with considerable power the works done on these structures are experimental and
conversion efficiency. In this paper, the performance of PCSs is cannot be analyzed by existing numerical models [5]. Thus,
investigated using a physics based analytical model considering
we intended to analyze the performance of PSCs using a
important parameters. Two basic structures (i.e., p-i-n and n-i-
p) of PSC are considered for this work to find out the optimal physics based analytical approach [6], which allows us to
design parameters. The changes of the short circuit current characterize the basic structures of PSCs with the effect of
density, open circuit voltage, efficiency along with the J-V different important physical parameters.
characteristics curves for both structures of PSCs are shown In this paper, we aimed at investigating the performances
here as performance indicating parameters. This analysis would of two different structures (i.e., p-i-n and n-i-p) of PSCs using
help to understand the basic physical parameters responsible an analytical model in order to determine the optimal design
for increasing the efficiency of PSCs and find out their optimal parameters for a given structure. First, the basic PSC structure
design parameters. parameters and the analytical model with the assumptions
Keywords— Perovskite Solar Cell, Generation rate, Open
that are made in the model are described. Then, the
Circuit Voltage, Absorber layer, front/back transport layer. performances of both PSC structures are presented by
changing different physical parameters and finally suggest
feasible optimal parameters for improving the efficiency.
I. INTRODUCTION
Due to the increasing power crisis of the present world, II. BASIC PEROVSKITE SOLAR CELL STRUCTURES
researchers are moving towards renewable energy sources. The original perovskite structure comes from calcium
Solar energy is the most abundant and environmentally titanium oxide (CaTiO3) and its general crystal structure can
friendly reliable energy source among all available renewable be written as ABX3 [7]. Where, A is a cation with lower
energy sources. Photovoltaic (PV) technology has been electronegativity and bigger size, small cation B is typically
considered the most auspicious ways to meet up the future divalent metal ion such as Pb2+, Sn2+ or Cu2+ while X is halide
energy demands as it can produce energy directly from ion (Cl-, Br- and I-) that is bonded to both A and B [7].
sunlight [1]. Because of the potential advantages of PV
technology, the necessity of cost effective and very efficient
organic-inorganic hybrid solar cells has tremendously
increased in recent years. Nowadays, Perovskite solar cells
(PSCs) based on organometallic halides have become an
emerging PV technology [2-3]. Perovskite materials have
drawn much attention to researchers due to their flexibility
regarding device fabrications, lower cost, improved
efficiency as well as simple structures. The rapid increment
of power conversion efficiency (PCE) in recent years has
made them an interesting and promising candidate for the
existing PV technology [3].
In order to understand the behavior of PV cells with
Perovskite material, it is necessary to develop basic models
that incorporates the possible parameters for both materials
and structures. Most of theoretical work on PSCs to date are
based on empirical formulas or numerical in nature [4, 5].
There have been many attempts made by the researches for
increasing the cell efficiency by changing materials of Fig. 1 Schematic representation of the (a) p-i-n and (b) n-i-p PCSs.

978-1-5386-9111-3/19/$31.00 ©2019 IEEE

Among all perovskites, Methyl ammonium lead iodide interface, and is the built-in potential across the absorber
(CH3NH3PbI3) draws huge attention because of its suitable layer. The efficiency of the designed PSC can be determined
optical and electronic properties favorable for PV technology by Eq. (11), which is the measure of the available electricity
[8]. In general, CH3NH3PbI3, an organo-metallic halide output from the cell that is converted from the fraction of
perovskite, plays the vital role in photoelectric conversion for incident solar power incident on the solar cell [10].
PSCs and considered to be the light absorber layer. The basic
structures of the PSC are shown in Fig. 1. Generally, a typical = (11)
.
cell consists of a perovskite absorber layer, a hole transport
layer (p-type), an electron transport layer (n-type), and front Here, η is the efficiency, Pp is the maximum output power
and back contacts (not shown in Fig. 1), arranged in mainly generation by the cell and PAM 1.5G is solar spectral irradiance
two configurations: p-i-n and n-i-p. In the structure PSCs (i.e. at AM 1.5G, which is 1 kW/m2. The above equations (i.e.
p-i-n), PEDOT: PSS is used as the front hole transport layer Eqs. 1 to 11) were solved in MATLAB environment in order
and Phenyl-C61-butyric acid methyl (PCBM) is the back- to get the output of PSCs with different parameters used in
electron transport layer, whereas the conventional structure the model.
(n-i-p) has TiO2 and Spiro-OMeTAD as the front electron
transport layer and the back-hole transport layer, respectively IV. PARAMERS USED FOR THE MODEL
[9].
There are different semiconductor material parameters that
are used in the model for different layers of PSCs are
III. MATHEMATICAL MODEL considered at a temperature 300 K. The value of is
Conventional models such as numerical or empirical taken as 23 mA/cm2; is ~ 100 nm; D = 0.05 cm2s-1 is
models cannot fully explain the operation of basic types of known for the used material system for both electrons and
PSCs. Thus, a physics based analytical model [6] is adapted holes [6] and q/kT is taken as 0.0259. Here, the contact
here to investigate the performances of basic PSC structures, resistances for both contacts (front end and back end) of PSCs
as shown in Fig. 1. in the model were neglected as we were primarily interested
The total current density-voltage characteristics of these to observe the intrinsic parameters of the PSCs.
two types of PSCs can be defined by the following equations
TABLE I. PARAMETERS FOR p-i-n AND n-i-p PSCs [6].
[6]:
Type p-i-n (Sample #1) n-i-p (Sample #2)
= × + × −1 (1)
Jf0 (mA/cm2) 2.7×10-13 1.6×10-17
= ( − ) (2)
Jb0 (mA/cm2) 4×10-13 4.8×10-17
= + (3) Vbi (V) 0.78 1
The parameters namely , , A, B and m is known as the Sf (cm/s) 2×102 1×104
model parameters. Here, ( ) is the dark diode current Sb (cm/s) 19.2 5.4
recombining at the front/back transport layer, is the
maximum generation, and q is the charge.
V. RESULTS AND DISCUSSION
The model parameters described here are the functions of
the material and structural parameters of the cell and can be A. Dark and Photo Current Density
asserted by the following equations [6]: Figure 2 and 3 shows the variation of dark current and
1 −1 photo current density with voltage for p-i-n and n-i-p PSCs,
= + (4)
respectively. The current remains almost constant with the
1 −1 increase of voltage up to 0.8 V and then decreases rapidly. It
= + (5) is also noted that the dark current is illumination independent
and light current determine the whole performance as it
1− depends on the illumination intensity.
= × − (6)
−
1− 5
= × − (7)
+
Current Density, J(mA/cm2)

0
, ( ) , and m can be expresses as following equations [6]
( − ) -5
= (8) Dark Current Density,
-10
( ) = (9)
× ( ) -15
Photo Current Density, Jphoto
= (10) -20
The physical parameters deduced here are , , ,
-25
, ( ) , , ( ) . Here, is material specific constant, 0 0.2 0.4 0.6 0.8 1
averaged over the solar spectrum, is the thickness of the Voltage, V(volt)
absorber layer, is the diffusion coefficient, ( ) is the Fig. 2 The variation of dark and photo current density with voltage in p-i-n
effective surface recombination velocity at the front/back PSC.
 5 thickness of the cell as it absorbs more photons which
produces more carriers in the absorber layer thereby increases
Current Density, J(mA/cm2)

0
the JSC. However, as the electric field decreases with the
-5 thickness of the absorber layer, the Voc also decreases with
Dark Current Density, Jdark
the thickness. For the both samples considered, efficiency of
-10 the PSC increases with the thickness to a particular point and
then decreases due to the decrease in electric fields. Thus,
-15 Photo Current Density, Jphoto
thickness optimization is necessary as the extra thickness
-20 does not give any benefits for PSCs.

-25 16
0
0.6 0.80.2 1 0.4 1.2
Voltage, V(volt) 15.6
Fig. 3 The variation of dark and photo current density with voltage in n-i-p
PSC. 15.2

Efficiency (%)
14.8
We used the parameters for sample 1 and 2 as shown in
Table-I. It is found that the Jsc, Voc and efficiency of sample 14.4
1 are 22.7 mA/cm2, 0.85 V and 15.7%, respectively. On the 14
other hand, these performance evaluating parameters are
13.6 sample #1
found to be 21.9 mA/cm2, 1.07 V and 15.4% respectively for sample #2
sample 2. Remembering all other parameter equal to the 13.2
values as shown in Table-I, the importance of absorber 200 250 300
350 400 450 500 550 600
thickness on cell performance can be explored in the next Thickness, t0 (nm)
section. Fig. 6 Behavior of efficiency by varying absorber thickness.

B. Effect of Absorber Thickness C. Effect of Built in Potential

-22.72 -21.5
-19.5 sample #1
sample #1
Jsc (mA/cm2) for sample #1

Jsc (mA/cm2) for sample #2

-20 -22.724 sample #2
sample #2 -21.6
-20.5
Jsc (mA/cm2)

-21 -22.728
-21.5 -21.7
-22.732
-22
-22.5 -21.8
-22.736
-23
-23.5 -22.74 -21.9
200 250 300 350 400 450 500 550 600 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4
Thickness, t0 (nm) Built-in potential, Vbi (V)

Fig. 4 Behavior of short circuit current density by varying absorber Fig. 7 Behavior of short circuit current density by varying built-in potential.
thickness.

1.2
1.115

1 1.065
Voc (V)

1.015
Voc (V)

0.8 0.965 sample #1

sample #1 sample #2
sample #2 0.915

0.6 0.865
200 250 300 350 400 450 500 550 600
Fig. 5 Behavior of open circuit voltage tby(nm)
Thickness, varying absorber thickness.
0 0.815
Fig. 5 Behavior of open circuit voltage by varying absorber thickness. 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4
Built-in potential, Vbi (V)
Thickness of the absorber layer is the most critical parameter
Fig. 8 Behavior of open circuit voltage by varying built-in potential.
for designing PSCs as it determines the maximum generation
of different carriers. The effects of thickness on Jsc, Voc and
The effects of built in potential on cell performances (i.e. JSC,
η for both p-i-n and n-i-p PSCs are shown in Fig. 4, 5 and 6,
VOC and η) are shown in Fig. 7, 8 and 9 respectively. With the
respectively. For both samples, the Jsc increases with the
increase in built in potential, the short circuit density Here both type PSC’s contain same absorber layer. So, their
increases exponentially for both samples. The Voc and variation of performance for photon absorption will be the
efficiency of the cell increases towards a particular point and same.
then saturates. While examining the intrinsic samples 1 and
2, it is noted that after saturation the average Voc of sample 1 17
is 0.3V smaller than that of sample 2. To improve the Voc, one
16.5
can increase the built-in potential Vbi by adjusting the band
alignment at the interface as well as increasing the doping of 16

Efficiency (%)
the transport layers.
15.5
20
15
19
14.5
18 sample #1
Efficiency (%)

14 sample #2
17
13.5
21 21.5 22 22.5 23 23.5 24
16
qGmax (mA/cm2)
sample #1
15
sample #2 Fig. 12 Behavior of efficiency by varying qGmax
14 E. Effect of Recombination Velocity
0.7 0.8
0.9 1 1.1 1.2 1.3 1.4
Built-in potential, Vbi (V) The effects of recombination velocity at the back side are
Fig. 9 Behavior of efficiency by varying built-in potential. depicted in Fig. 13, 14 and 15. In general, it is observed that
any potential improvement in the back selective blocking
D. Effect of Generation Rate (Gmax.) layer offers very little gain, since most of the photo-
generation occurs close to the front contact. It has to be noted
-19.5
that for both type of materials, the recombination velocity at
sample #1 the back layer has a little impact on cell performance.
-20
sample #2 -22.72669 -21.7273
-20.5
-21
Jsc (mA/cm2) for sample #1
Jsc (mA/cm2)

-21.72731
-21.5 -22.7267
-22
-21.72732
-22.5 -22.72671
-23 -21.72733
-23.5
-22.72672
-24 sample #1 -21.72734
21 21.5 22 22.5 23 23.5 24
qGmax (mA/cm2) sample #2
-22.72673 -21.72735
0 5 10 15 20 25
Fig. 10 Behavior of short circuit current density by varying qGmax.
Recombination velocity at back side, Sb (cm/s)
0.8635 1.055
Fig. 13 Behavior of short circuit current density by varying
0.863 1.054 recombination velocity at back side.
Voc (V) for sample #1

Voc (V) for sample #2

0.8625 1.053 1.1

1.05
0.862 1.052
1 sample #1
0.8615 1.051 sample #2
0.95
Voc (V)

0.861 1.05
0.9
sample #1
0.8605 1.049 0.85
sample #2
0.86 1.048 0.8
21 21.5 22 22.5 23 23.5 24
0.75
qGmax (mA/cm2)
0.7
Fig. 11 Behavior of open circuit voltage by varying built-in potential. 0 5 10 15 20 25
The effects of the position independent photon absorption on Recombination velocity at back side, Sb (cm/s)
cell performances are shown in Fig. 10, 11 and 12,
Fig. 14 Behavior of open circuit voltage by varying recombination
respectively. With the increase in photon absorption, more
velocity at back side.
photoelectrons generate which increases short circuit current
density linearly. As for both samples Jsc and Voc increases
with the increment of qGmax, the efficiency also increases.
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Efficiency (%) for sample #1

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