Design and Device Modeling of Lead Free CsSnI3 Perovskite Solar Cell

Yogesh Kumar; Sweta Minj; Naman Shukla; Sanjay Tiwari

doi:10.52228/JRUB.2022-35-1-4

Journal of Ravishankar University

Pt. Ravishankar Shukla University, Raipur, Chhattisgarh

PART-B

(SCIENCE)

ISSN: 0970-5910

Article in HTML

Submit Article

Design and Device Modeling of Lead Free CsSnI3 Perovskite Solar Cell

Author(s): Yogesh Kumar, Sweta Minj, Naman Shukla, Sanjay Tiwari

Email(s): naman.shukla43@gmail.com

Address: School of Studies in Electronics and Photonics, Pt. Ravishankar Shukla University, Raipur-492010, C.G., India

Published In: Volume - 35, Issue - 1, Year - 2022

Keywords:

Cite this article:
Kumar, Minj, Shukla and Tiwari (2022). Design and Device Modeling of Lead Free CsSnI3 Perovskite Solar Cell. Journal of Ravishankar University (Part-B: Science), 35(1), pp. 25-34.

View PDF

Design and Device Modeling of Lead Free CsSnI₃ Perovskite Solar Cell

Yogesh Kumar, Sweta Minj, Naman Shukla, Sanjay Tiwari

School of Studies in Electronics and Photonics, Pt. Ravishankar Shukla University, Raipur-492010, C.G., India

*Corresponding author: naman.shukla43@gmail.com

Abstract:

Research of lead-free Perovskite based solar cells has gained speedy and growing attention with urgent intent to eliminate toxic lead in Perovskite materials. The main purpose of this work is to supplement the research progress with comparative analysis of different lead-free Perovskite based solar cells by numerical simulation method using solar cell capacitance simulator (SCAPS-1D) software. The environmental friendliness and excellent thermal stability proves Cesium Tin Iodide (CsSnI₃) as one of the promising materials for the commercialization of the Perovskite solar cells. However, CsSnI₃ solar cells suffer from poor efficiency due to having low open-circuit voltage, V_OCattributed to poor absorber film quality as well as energy level mismatch at the interfaces between different layers like transparent front contact. The architecture of the solar cell is n-i-p device structure acts as light CsSnI₃ absorber active layer, TiO₂ as electron transport layer and Spiro-OMeTAD as hole transport layer with device structure FTO/ TiO₂/CsSnI₃/ Spiro-OMeTAD /Au. The open circuit voltage V_oc, short circuit current density I_sc, fill factor and power conversion efficiency V_oc=1.09V, J_sc=28.85mA/cm², FF=88.65%, eta=28.09%, V_MPP=0.99V, J_MPP=28.15 mA/cm² respectively.

Keywords — Perovskite Solar Cell, Lead-free, CsSnI₃, SCAPS 1D

Introduction:

Perovskite solar cells have experienced a major leap in their power conversion efficiency (PCE) just over a decade due to their very simple manufacturing process, comparatively low processing cost, high absorption coefficient, low surface recombination rates and relatively high efficiency. It has increased from 3.8% in 2009 reported by Miyasaka and his colleagues in 2009 (Kojima et al., 2009) to 25.5% till date (NREL, Best research-cell efficiencies) in single-junction architectures, which is quite close enough to the crystalline silicon solar cells at 26.7%. The hybrid organic-inorganic perovskites have opened new doors towards more efficient light harvesting materials. Owing to the property of tunable frequency, these solar cells can be quite effective in absorbing different light frequencies by different layers which can lead to a boost in their efficiencies unlike the conventional solar cells. Despite this, lead based perovskites have two major challenges: a) poor stability which is being addressed by improved device engineering and encapsulation as well as incorporating the use of perovskites, b) high toxicity that is raising a concern on an environmental level. Lead free perovskite materials, which are non-toxic and are also being looked upon as another alternative. These lead free materials will be a preference in the solar cell market which will help in commercialization of perovskite solar cells if they do not compromise with the device performance. Ideally, Pb-free perovskites when used as light harvesting layers in solar cells, should have low toxicity, high optical absorption coefficients, low exciton-binding, narrow direct band gaps, high mobilities. Perovskites in the form of double perovskites, some Sn/Ge based halides, and also some Bi/Sb-based halides with perovskite-like structure show fascinating properties and are low-toxicity materials. Up to 2020, the highest efficiency for Sn-based perovskites has been reported to have reached 13.24%. In these Pb-free perovskite materials, comparatively only Sn-based PSCs have shown very promising performance. In Sn-based PSCs, certain factors like the poor air-stability caused due to quick oxidation of Sn₂⁺ leading to increased recombination losses, small formation energy of vacancies, high intrinsic carrier density etc. leads to poor device performance as compared to their corresponding lead-based analogues. The anti-bonding coupling between Sn-5s and I-5p is comparatively weaker in FASnI₃ (FA = CH (NH₂)₂) than CsSnI₃ and MASnI₃ as a result of the larger ionic size of FA which is also the reason behind the increase in formation energies of Sn-vacancies. Along with experiments, simulation also plays a vital role in analyzing various properties of these materials and the corresponding performance parameters for various such materials. This work aids in studying the relation of the properties with the parameters, comparing multiple materials with the help of theoretical analysis by designing a device model. Here, a comparative study of various Pb-free perovskites on a similar configuration is done which helps us know about the distinguishing properties, their impacts on device performance and further work for achieving high efficiencies for Pb-free perovskites

The organic-inorganic halide perovskite (ABX₃) solar cells are emerging as the best contender for futuristic photovoltaic energy harvesting process, which is evident from its tremendous growth of achieving power conversion efficiency as high as 25.2% reported form single-cell till to-date. Both the natural environment and humans. Therefore, there has been growing interest in the development of alternative perovskites that use Sn instead of Pb, such as CsSnI₃. Tin-based halide perovskite materials have been successfully employed in lead free perovskite solar cells. Recently, several studies have revealed that the substitution of the methyl ammonium cation by cesium (Cs) in the perovskite structure could significantly enhance its thermal stability. Notwithstanding that the high-performance perovskite cells are dominated by lead (Pb) based materials like Methyl Ammonium Lead Halide, MAPbX₃ (Shukla et al., 2021 and gopal et al., 2020) or Formamidinium Lead Hallie (FAPbX₃), the environmental impact of Pb as well as high bandgap of these perovskite materials have always made researchers think of its environmentally benign and low bandgap options, tin (Sn) based perovskites like MASnX₃ . Apart from this, inorganic cations like Cesium (Cs) have been considering as the substitute of the organic counter parts because of the instable ambient/outdoor performance of MAPbX₃ and FAPbX₃ due to the fragmentation of the organic components . Thus Cesium Tin Iodide, CsSnI₃ may be considered as one of the viable choices for the commercialization of perovskite solar cells. However, CsSnI₃ based solar cells suffer from lower efficiency. The stable and efficient perovskite solar cells can be developed through optimization of the solar cell device through experiments supported by data which is obtained by optical and electrical simulations. In this research work, the numerical simulation of the CsSnI₃ based perovskite solar cell was done by using Solar Cell Capacitance Simulator (SCAPS-1D). It is a one dimensional solar cell simulator based on the drift diffusion physical model (Burgelman et al., 2000).simulation of PSC. This software tool has executed the semiconductor equation, the continuity equation of carrier, Poisson equation, carrier transport equations etc.

The SCAPS software gives us the results by solving the basic semiconductor equations, Poisson equations, the continuity equations for electrons and holes and other carrier transport constraints (Burgelman et al.,2013). Organic metal halide perovskite is used as active layer in this simulation. Device simulations have been performed according to the parameters given in the literature summarized in Table 1 (Lin et al., 2014; Hima et al., 2019; Calado et al., 2016; Isoe et al., 2020).The n-i-p device structure is FTO/ TiO₂/ CsSnI₃/ Spiro-OMeTAD /Au. For optimized design of the solar cell for above structure, short circuit current density J_sc, open circuit voltage V_oc, fill factor FF and efficiency are V_oc= 1.09V, J_sc=28.85mA/cm², FF= 88.65%, eta= 28.09%, V_MPP=0.99 V, J_MPP=28.15 mA/cm²

FTO

TiO₂

CsSnI₃

Spiro-OMeTAD

Figure 1. Architecture of simulated model

Table 1: Simulated Parameters

Parameter	Spiro-OMeTAD	CsSnl₃	TiO₂	FTO
Thickness(nm)	0.500	0.300	0.200	0.030
Band gap (eV)	3.170	1.270	3.200	3.500
Electron affinity(eV)	2.050	4.470	4.260	4.500
Dielectric Permittivity	3.000	10.590	9.0	10
CB effective density of States(1/cm³)	2.200e+18	1.580e+19	2.200e+18	2.200e+18
VB effective density of States(1/cm³)	1.800e+19	1.470e+18	2.00e+18	1.800e+19
Electron thermal Velocity(cm/s)	1.00e+7	1.00e+7	1.00e+7	1.00e+7
Hole thermal velocity (cm/s)	1.00e+7	1.00e+7	1.00e+7	1.00e+7
Electron mobility(cm²/Vs)	2.00e-4	4.370e+0	2.00e+1	1.00e+2
Hole mobility(cm²/Vs)	2.00e-4	4.370e+0	1.00e+1	2.500e+1
Shallow uniform donor density N_D(1/cm³)	0	5.00e+19	1.00e+6	1.00e+20
Shallow uniform acceptor Density N_A(1/cm³)	2.000e+19	0	0	0
Defect Density (1/cm³)	0	1.000e+15	0	0

Figure 2: V-I graph of Perovskite CsSnI₃Solar cell

Result and discussion

Numerical modeling was carried out using 1D-SCAPS software and including various material proprieties given in Table-1. Firstly, the p-i-n solar cell structure, FTO/ Spiro-OMeTAD /CsSnI₃ /TiO₂/Au is studied and analyzed. Figure. 2 plots the J-V characteristics of both simulated and experimental Sn-based perovskite solar cell structure measured under reverse voltage. As can be seen from the Figure. 1, the obtained simulated results are very close to experimental ones taken from literature.

FTO/ Spiro-OMeTAD /CsSnI₃ /TiO₂/Au, based on Sn-perovskite material and corresponds to the layer thicknesses of 0.5, 0.3 and 0.2 micrometer for HTL, PAT and ETL, respectively. Figure. 2 displays the variation of J-V characteristic of the Sn -perovskite solar cell. The photovoltaic parameters V_oc=1.09V, J_sc=28.85mA/cm², FF=88.6587%, eta=28.09%, V_MPP=0.99V, J_MPP=28.15mA/. It is necessary to carry out an optimization process of the perovskite device. This is can be down by varying the diverse layer thicknesses, absorber, HTL and ETL layers. In this context, the optimization process consists to fix two-layer thicknesses and vary the remaining one. Then, in each case we select the layer CsSnI₃ thickness that gives the optimal PCE value. Figure. 3 shows the optimized J-V characteristics of the Sn -based perovskite solar cell. It is evident that the optimized perovskite device shows a noticeable enhancement in PCE from 17.24% to 29.33%. Sn-based perovskite device shows analogous photovoltaic performance comparable to Sn-based perovskite device. Using the same optimization method mentioned above, our simulation is performed on the power conversion efficiency as function of absorber layer thickness, temperature, band gap, electron affinity, defect density of absorbent layer in order to find the optimum values. The optimized value of absorber layer thickness, temperature, band gap, electron affinity gives higher PCE. Evidently, the PCE increases with increasing of absorber thickness and then decreases after reaching a specified value as shown in Figure. 3. This increasing is due to more photons absorbed by carrier concentration in this layer creating more electron hole pairs and led to high short-circuit current density in the device. In addition, PCE is measured for different temperature and it is noted that with increase band gap efficiency is decreases as shown in Figure. 4, measurement of PCE for different electron affinity is carried out and it is noted that with increase in electron affinity is increased and decreased it works well between 4-4.5 as shown in Figure. 5, measurement of PCE for different Temperature is carried out and it is noted that with increase in Temperature efficiency is decreases and it works well between 300k-375k as shown in Figure. 6, measurement of PCE for different defect density is carried out and it is noted that with increase in defect density efficiency is decreases and it works well between 10¹⁴ -10¹⁵ as shown in Figure. 7.

Figure 3: J-V Characteristics with different thickness of CsSnI₃ Perovskite active layer

Figure 4: Response of J-V Characteristics with different band gap (tunable range) of CsSnI₃ Perovskite active layer

Table 2: J-V Characteristics parameters at different thickness of CsSnI₃

Thikness	Voc	Jsc	FF	eta
0.100	1.11	17.404	89.01	17.24%
0.200	1.104	25.236	88.74	24.745%
0.300	1.098	28.850	88.658	28.094%
0.310	1.097	29.071	88.657	28.291%
0.320	1.097	29.271	88.654	28.469%
0.330	1.096	29.453	88.655	28.629%
0.400	1.092	30.287	88.636	29.326%
0.500	1.087	30.504	88.441	29.339%

Table 3: J-V Characteristics parameters with different band gap (tunable range) of CsSnI₃

Band gap	J_sc(mA/cm²)	V_oc(V)	FF	PCE(%)
1.20	31.322	1.030	88.25	28.47 %
1.23	30.48	1.039	88.36	28.55 %
1.26	29.21	1.088	88.69	28.20 %
1.27	28.85	1.098	88.65	28.09 %
1.271	28.82	1.099	88.64	28.09 %
1.278	28.636	1.105	88.66	28.08 %
1.28	28.576	1.107	88.67	28.07 %
1.29	28.245	1.117	88.77	28.02 %

Figure 5: Recorded J-V Characteristics of the device with variation of temperature

Table 4: J-V Characteristics parameter at different temperature

Temperature (K)	V_oc(V)	J_sc(mA/cm²)	FF	PCE
300	1.098	28.850	88.658	28.094 %
325	1.076	28.920	87.914	27.360 %
350	1.053	28.980	86.970	26.548 %
375	1.030	29.032	86.130	25.757 %
400	1.006	29.078	85.248	24.947 %
425	0.982	29.119	84.234	24.093 %
450	0.957	29.155	83.312	23.258 %
475	0.932	29.188	82.275	22.389 %

Table 5: J-V Characteristics parameters at different electron affinity value

Electron affinity(eV)	V_oc(V)	J_sc(mA/cm²)	FF	PCE(%)
4.0	1.093	28.429	88.517	27.508 %
4.1	1.097	28.803	88.803	28.090 %
4.17	1.098	28.845	88.804	28.129 %
4.2	1.098	28.848	88.802	28.134 %
4.27	1.098	28.851	88.795	28.136 %
4.37	1.098	28.851	88.767	28.128 %
4.47	1.098	28.850	88.658	28.094 %
4.5	1.098	28.850	88.574	28.067 %

Figure 6: Response of J-V Characteristics at different electron affinity

Figure 7: The role of defect density in CsSnI₃Perovskite solar cells

Table 6: Recorded parameters at different defect density of CsSnI₃

Defect density	Voc	Jsc	FF	PCE(%)
1E+14	1.158	29.687	89.25	30.68 %
1.1E+15	1.096	28.760	88.65	28.09 %
1.2E+16	1.032	21.454	87.56	19.38 %
1E+17	0.968	7.114	86.01	5.92 %
1.3E+18	0.887	1.154	83.14	0.85 %
1.5E+19	0.821	0.323	77.62	0.20 %
1E+20	0.771	0.142	71.64	0.07 %
1E+21	0.770	0.048	68.73	0.02 %

Acknowledgement

I am thankful for research facilities provided by Photonics Research Laboratory, School of Studies in Electronics and Photonics, Pt. Ravishankar Shukla University, Raipur, Chhattisgarh, India. I would like to acknowledge Dr. Marc Burgelman and the researcher team associated with Department of Electronics and Information Systems, University of Gent, Belgium for providing the simulation software SCAPS-1D.

Reference

Burgelman, M., Decock, K., Khelifi, S. and Abass, A. (2013). Advanced electrical simulation of thin film solar cells. Thin Solid Films. 535, 296-301.

Burgelman, M., Nollet, P. and Degrave, S. (2000). Modelling polycrystalline semiconductor solar cells. Thin Solid Films. 361-362, 527-532.

Burschka, J., Pellet, N., Moon, S.J., Baker, R.H., Gao, P., Nazeeruddin, M.K. and Grätzel, M. (2013). Sequential deposition as a route to high-performance perovskite-sensitized solar cells. Nature 499, 316–319.

Calado, P., Telford, A.M., Bryant, D., Li, X., Nelson, J., O'Regan, B.C. and Barnes, P. R.F. (2016), Evidence for ion migration in hybrid perovskite solar cells with minimal hysteresis, Nat. Commun. 7, 13831.

Correa-Baena, J.-P. et al. The rapid evolution of highly efficient perovskite solar cells. Energy Environ. Sci. 10, 710-727 (2017).

Correa-Baena, J.-P. et al. Promises and challenges of perovskite solar cells. Science 358, 739-744 (2017).

Jena, A. K., Kulkarni, A. & Miyasaka, T. Halide perovskite photovoltaics: background, status, and future prospects. Chem. Rev. 119, 3036-3103 (2019)

Jiang, X. et al. “Ultra-high open-circuit voltage of tin perovskite solar cells via an electron transporting layer design”, Nat. Common., Vol. 11, pp. 1245, 2020.

Kojima, A., Teshima, K., Shirai, Y. & Miyasaka, T. Organometal halide perovskites as visible-light sensitizers for photovoltaic cells. J. Am. Chem. Soc. 131, 6050-6051 (2009)

Krishna, B. G., Rathore, G. S., Shukla, N., and Tiwari, S. (2020). Perovskite solar cells: A review of architecture, processing methods, and future prospects, in: Khan I., Khan A. (Eds.), Hybrid Perovskite Composite Materials Design to Applications. Woodhead Publishing, Elsevier, Duxford, pp. 375-412.

Kumar, M. H. et al. Lead‐free halide perovskite solar cells with high photocurrents realized through vacancy modulation. Adv. Mater. 26, 7122- 7127 (2014)

Martin A. Green et al., “Solar cell efficiency tables (version 56)”, Prog Photovoltaic Res Apply, vole. 28(7), pp629638, June 2020

Ning Wang et al., “Heterojunction-Depleted Lead-Free Perovskite Solar Cells with Coarse-Grained B-γ-CsSnI₃ Thin Films”, Advance Energy Materials, vole. 6(24), pp. 813–820, December 2016.

National Renewable Energy Laboratory, Best research-cell efficiencies. https://www.nrel.gov/pv/assets/pdfs/best-research-cell-efficiencies-rev220126.pdf

Shi, D., Zeng, Y. and Shen, W. (2015). Perovskite/c-Si tandem solar cell with inverted nanopyramids: realizing high efficiency by controllable light trapping. Sci Rep 5, 16504.

Shukla, N., Lal, D., and Tiwari, S. (2021). Investigation on Design and Device Modeling of High Performance CH₃NH₃PbI_3-xCl_x Perovskite Solar Cells. Journal of Ravishankar University (Part-B: Science), 34(1), pp. 58-63.

Tan, Z.K., Moghaddam, R.S., Lai, M.L., Docampo, P., Higler, R., Deschler, F., Price, M., Sadhanala, A., Pazos, L.M., Credgington, D., Hanusch, F., Bein, T., Snaith, H.J. and Friend, R.H. (2014). Bright light-emitting diodes based on organometal halide perovskite. Nat Nanotechnol. 9(9):687-92.

Tiwari, S., Yakhmi, J.V., Carter, S. and Scott, J.C. (2018) Optimization of Bulk Heterojunction Organic Photovoltaic Devices. Handbook of Ecomaterials. Springer, Cham.

Yang, W.S, Park, B.W., Jung, E.H., Jeon, N.J., Kim, Y.C., Lee, D.U., Shin, S.S., Seo, J., Kim, E.K., Noh, J.H. and Seok, S.I. (2017).

Iodide management in formamidinium-lead-halidebased perovskite layers for efficient solar cells. Science 356, 1376.

Yang, W.S., Noh, J.H., Jeon, N.J., Kim, Y.C., Ryu, S., Seo, J. and Seok, S.I. (2015) High-performance photovoltaic perovskite layers fabricated through intramolecular exchange, Science 348, 1234.

Zhou, H., Chen, Q., Li, G., Luo, S., Song, T.B., Duan, H.S., Hong, Z., You, J., Liu, Y. and Yang, Y. (2014). Interface engineering of highly efficient provskite solar cells. Science, vol. 345, 542-546.

Related Images: