J. Nig. Soc. Phys. Sci. 5 (2023) 1222

Journal of the
Nigerian Society

of Physical
Sciences

Study of the passivation of defects in the perovskite cell:
application to Sahelian climate conditions

Essodossomondom Anatea,∗, N’Detigma Kataa,b, Hodo-Abalo Samaha, A. Seidou Maigab

aFaculté des Sciences et Techniques, Université de Kara, Kara, Togo
bLaboratoire Electronique, Informatique, Télécommunication et Energies Renouvelables, Université Gaston Berger, Saint-Louis, Sénégal

Abstract

This article is devoted to the study of the performance of the photovoltaic cell based on perovskite (MAPbI3) in real conditions of sub-Saharan
Africa. A model of this cell has been made taking into account the integration of defects at the interfaces. After a study of the sensitivity of these
defects, a passivation layer was introduced at the interface to improve the performance of the cell. The influence of temperature and irradiance
on the performance of perovskite cells was studied on the one hand with defects at the interfaces and on the other hand with the integration of
a passivation layer of defects. The results show a decrease of the performance ratio for the non-passivated cell due to the defects present at the
interfaces of the said cell. The models developed under SCAPS-1D were validated by applying it to a real module found in the literature under the
same conditions. The performance calculation shows a satisfactory qualitative and quantitative agreement. The results relative to the performance
ratios obtained for the simulated models show that perovskite is on the right track for a potential future candidacy to the most suitable technologies
for sub-Saharan Africa.

DOI:10.46481/jnsps.2023.1250

Keywords: Modeling, perovskite solar cells, interface defects, performance ratio.

Article History :
Received: 30 December 2022
Received in revised form: 23 March 2023
Accepted for publication: 30 March 2023
Published: 14 May 2023

c© 2023 The Author(s). Published by the Nigerian Society of Physical Sciences under the terms of the Creative Commons Attribution 4.0 International license

(https://creativecommons.org/licenses/by/4.0). Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.

Communicated by: K. Sakthipandi

1. Introduction

Africa has an almost unlimited potential for solar energy,
estimated at about 10 TW [1]. However, Africa is among the
regions in the world with the lowest coverage of electrical en-
ergy. Photovoltaics being the ideal alternative, solar fields are
covering more and more surfaces using first generation modules
which are relatively expensive and which moreover see their
yields decrease under the influence of the temperature. Stud-
ies have shown the production capacity of thin-film technol-

∗Corresponding author tel. no: +22893089314
Email address: edso.anate@gmail.com (Essodossomondom Anate)

ogy compared to first generation technology for sub-Saharan
climate conditions [2,3]. Thus, this study is situated in the con-
text of predicting the photovoltaic production under real sub-
Saharan conditions of third generation thin film modules based
on perovskite. The challenge is to evaluate the influence of cli-
matic factors, in particular temperature, on the photovoltaic per-
formance of these solar photovoltaic modules.

The interest of this technology is its very high efficiency of
25.5% in 2020 [4–6]. In addition, perovskite is a low-cost ma-
terial with exceptional structural and optoelectronic properties.
Tolerant in volume defects [6–8], it is not so when it comes to
defects at the interfaces which in addition to lowering the yield,

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Anate et al. / J. Nig. Soc. Phys. Sci. 5 (2023) 1222 2

makes it less stable in the long term. Of neutral, acceptor or
donor nature, once at the interfaces, they significantly degrade
the performance of the cell [7]. The most effective technique
to minimize the influence of defects is passivation which uses
materials with specific properties. Organic compounds with the
carbonyl group are widely used to passivate perovskite cells [9]
by exploiting the coordinated bonds based on Lewis’s acid-base
chemistry [10–12].

Wang et al. showed the passivation ability of theophylline
(C7H8N4O2) on perovskite cells [9]. In this work, we exam-
ine the performance precisely the performance ratio of per-
ovskite cells under sub-Saharan African conditions by simu-
lation. Three perovskite modules, one of which is real [13]
and two others modeled under SCAPS, are simulated under the
same conditions. The purpose of the study of the latter two is to
evaluate the impact of defects when the modules are operated
in real conditions at high temperatures.

2. Methodology

We first model the cell under the SCAPS-1D software ver-
sion 3.3.1.0 following the FTO/ETL/perovskite/HTL/Au struc-
ture by integrating at the ETL/perovskite and perovskite/HTL
interfaces the neutral, acceptor and donor defects of the or-
der of 108 - 1011 cm−2 following Street et al. [8,14]. These
three types of defects come either from vacancies (Vx) such as
VMA, VPb, VI , or interstitials (Xi) like MAi, Pbi, Ii, or substi-
tutions (Xy) such as MAPb, PbMA, MAI , PbI , IMA, IPb of the
constituents (x or y= MA, Pb, I) [7] of the perovskite or of for-
eign elements. They can carry different electric charges behav-
ing as electron acceptor, donor or neutral. Then a passivation
layer based on theophylline is introduced following the struc-
ture FTO/ETL/Theophylline/perovskite/HTL/Au. The cell with
defects at interfaces and the one with passivation layer were
used to model tow modules. The data (Voc, Isc and Pmax)
from these models in addition to those from the real module
which is from literature [13] are used in the hybrid Levenberg-
Marquardt-analytical extraction program proposed by Kata et
al. to extract the parameters (Iph, I0, n, Rs and Rsh) needed
for the simulation under LTSpice [15]. Finally, the sub-Saharan
temperature and sunshine conditions are entered into the LT-
Spice module through the translation relations [15]. As an out-
put, a current-voltage characteristic under real conditions is ob-
tained for each measurement. Table 1 provides the information
on module modeling considerations with reference to the real
module. Figure 1 shows the method for evaluating the perfor-
mance ratio of the module.

Solar irradiance and temperature data are taken from a mea-
surement site in Ouagadougou (Burkina Faso) due to the un-
availability of that site in Kara (Togo) at the moment.

These data such as temperature and irradiance are measured
at the same time as module I-V characteristic, module volt-
age and module current by using multimeters simultaneously
whereas a pyranometer was used to measure the irradiance as
describe by Kata et al. [15]. Two days are chosen to represent
the dry season for one and the rainy season for the other. The

Figure 1: Diagram of the performance ratio evaluation

Figure 2: Effects of acceptor defects density at ETL/Absorber interface

performance evaluation is based on the calculation of the per-
formance ratio (PR) of the three modules. The real efficiency
(real) of the LTSpice module is determined for each day’s mea-
surement using equation 1. The performance ratio allows com-
parison of this performance between the three modules under
the same conditions. This ratio refers to the ratio of the real ef-
ficiency under real conditions (real) to the efficiency under Stan-
dard Test Conditions (STC) (STC) in equation 2. This Standard
Test Conditions include the temperature of 25◦C, AM1.5 and
an irradiance of 1000 Wm−2.

real =
Pmreal

S ∗ Greal
, (1)

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Anate et al. / J. Nig. Soc. Phys. Sci. 5 (2023) 1222 3

Table 1: Characteristics of the simulated modules

PV module base on : Passivated cell Cell with defects Real cell
Number of cells 55 in series 55 in series 55 in series
Efficiency (%) 27.87% 24.73% 17.9%

Voc (V) 71.61 63.86 58.7
Isc (A) 0.325 0.323 0.323

Vmax (V) 64.9 58.3 48.42
Imax (A) 0.318 0.314 0.298
Pmax (W) 20.6 18.25 14.43

Figure 3: Effects of neutral defect density at Abs / HTL interface

Figure 4: I-V characteristic of the simulated module

PR = real
S T C
, (2)

where Pmreal is the maximum power under real conditions, S
the surface of the module and Greal is the real condition solar
irradiance.

Figure 5: Energy band diagrams without (a, b) and with (c, d) passivation

3. Results and discussion

We studied the sensitivity of the defects at both interfaces
varying from 1 to 1015 cm−2. The drop in performance is felt
from 1011 cm−2 at the ETL/perovskite interface for the three
types of defects. Figure 2 illustrates this effect for the acceptor
type with a drastic drop in Voc of 0.66 V, a Jsc of 4.53 mAcm−2,
a FF of 78.83% and a yield of 2.35% at 1015 cm−2.

At the perovskite/HTL interface, the drop already starts at
106 cm−2 for all three types as well. At the perovskite/HTL in-
terface (Figure 3), we note a decrease in Voc of 0.142 V and
Jsc of 1.915 mAcm−2 for neutral defect densities ranging from
106 to 109 cm−2 which results in the loss of 2.34% of the FF
and especially the yield which falls from 27.17% to 21.66% or
a loss of 5.51%. This overall decrease can be explained by a
low mobility of holes and therefore a low collection at the in-
terface due to the introduction of larger neutral defects. Similar
observations are made at other interfaces.

By applying the theophylline defect passivation layer whose
electronic properties are derived from the work of Ejuh et al.
[16], the results are presented in graphical form. Figure 4
shows the I-V characteristics of the ideal, passivated and non-
passivated cells. A significant improvement in the Voc of the
passivated cell compared to the non-passivated one is observed.
This increase provides information about the recombination re-
duction.

We also observed the behavior of the band diagrams of the
two modeled cells. The presence of defects (charged point de-

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Anate et al. / J. Nig. Soc. Phys. Sci. 5 (2023) 1222 4

Figure 6: Comparison of the electrical characteristics of the cell without and with passivation

Figure 7: Performance ratio for a clear day (dry season)

fects) at the interfaces manifests itself on the band diagram as
unfavorable band edge curvature (possibly due to unintentional
doping effect)[7,17]. Passivation reduced this unfavorable band
curvature by eliminating the defects and their effect at the inter-
face [17] to promote better performance such as improved open

Figure 8: Performance ratio for an overcast day (Rainy season)

circuit voltage by widening the potential barrier at the junction.
Figures 5.a and 5.b show the band diagrams at equilibrium and
at Voc for a cell with defects, respectively, followed by Figures
5.c and 5.d at equilibrium and at Voc for a passivated cell, re-
spectively.

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Anate et al. / J. Nig. Soc. Phys. Sci. 5 (2023) 1222 5

Here we present the performance of the modeled cells be-
fore and after passivation. The effect of the three types of de-
fects at the perovskite / HTL interface is shown by a decrease
in the graphs of Figure 6 from 106 cm−2. The effect of passiva-
tion on the other hand is illustrated by straight lines giving as
information the annihilation of the effect of these defects.

We present here on Figures 7 and 8 the production capacity
in prediction of the performance under real conditions in Sub-
Saharan Africa. The choice of two days for our study reflects
the rainy season for the overcast day and the dry season for the
clear day. The performance ratio of the three modules reaches
80% over most of the day for both days (Figures 7 and 8). For
the clear-sky day, this ratio exceeds 90% between 9 a.m. and 3
p.m., a period during which there is often high irradiation. The
strong dependence of the power of the module on the irradia-
tion means that one could recover 90% of the power Pmax S T C
on more than half of the day, this one could even reach 94%
and 96% respectively for the modules with not passivated and
passivated cells then 98% for the real module. During the same
period, high module temperatures exceeding 47◦C are recorded.

However, the highest PRs are obtained during this period,
moreover, there is no decrease in the ratio for the highest mod-
ule temperatures of the day which are about 68 ◦C. This means
that the perovskite solar modules show only a small decrease
in efficiency with high temperature. The real module and the
module with passivated cells have very close ratios for both
day conditions. However, the non-passivated cell shows much
lower ratios over all the measurements. This low ratio is ex-
plained by the presence of defects at the interfaces of the cells
of this module.

The evolution of the performance ratios of the real and pas-
sivated modules shows the relevance of the simulated models.
Moreover, by observing the ratios of the two days we can say
that the program responds well to the variations of the solar ir-
radiation. Referring to Figure 8, it can be seen that perovskite
modules have good ratios for overcast skies, which is an asset
for some regions of sub-Saharan Africa that have longer rainy
seasons with irregular irradiation. This interesting performance
of perovskite allows us to consider perovskite as a potential fu-
ture candidate of the most suitable technologies for the sub-
region.

4. Conclusion

This study was devoted to the evaluation of the performance
of perovskite cells under the conditions of sub-Saharan Africa.
Different defects at the interfaces, namely neutral, acceptor and
donor types, have been studied on the perovskite cell mod-
eled under SCAPS-1D. The simulation of the model showed a
strong sensitivity of the defects at the ETL/perovskite and per-
ovskite/HTL interfaces of the cell. The results also show the
performance improvement by introducing a passivation layer.
The simulation of the perovskite solar cell in real conditions of
sub-Saharan Africa is done. The hybrid Levenberg-Marquardt-
analytic parameter extraction method proposed by Kata et al.

was used to extract the modeling data under LTSpice. The per-
formance ratio of perovskite cells can reach 98% at module
temperatures around 68 ◦C in sub-Saharan African conditions.
These results are quite interesting and encouraging for a possi-
ble use in the subregion.

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