International Journal of Energetica (IJECA) https://www.ijeca.info ISSN: 2543-3717 Volume 5. Issue 1. 2020 Page 27-30 .http://dx.doi.org/10.47238/ijeca.v5i1.119. June 2020 Page 27 Enhancing of CH3NH3SnI3 based solar cell efficiency by ETL engineering. Abdelkader Hima 1* , Abderrahmane Khechekhouche 2,3 , Imad Kemerchou 3,4 1 Department of Electrical Engineering, Fac. Technology, University of El Oued, El Oued, 39000, ALGERIA 2 Faculty of technology, El-Oued University, ALGERIA 3 Laboratory ofAnalysis and Control of Energy Systems and Networks, University Thelidji Amar of Laghouat, ALGERIA 4 Materials Science and Engineering Program, State University of New York at Binghamton, Binghamton, New York 13902, USA E-mail*: abdelkader-hima@univ-eloued.dz Abstract – Solar cells based on organic-inorganic perovskites (PVK) are the subject of several researches in laboratories around the world. One of the most promising hybrid perovskite is the methylammonium lead tri-iodide MAPbI3 that is suitable for sun light harvesting. But the MAPbI3 is a toxic material, so in this paper is proposed another nature friendly candidate which is the methylammonium tin tri-iodide MASnI3. The proposed material is inserted into an n-i-p heterojunction solar cell which structure is electron transport layer (ETL)/PVK/hole transport layer (HTL). The used HTL is the PEDOT: PSS in combination with one of two ETLs which are the PCBM and the IGZO. Simulation efforts using 1D SCAPS was carried. It is found that IGZO ETL based solar cell yields a higher power conversion efficiency (PCE) compared with PCBM ETL based solar cell in the same thickness. Keywords: Perovskite, Solar cell, SCAPS Software, PCE, PCBM, IGZO. Received: 03/04/2020 – Accepted: 12/06/2020 NOMENCLATURE ABBREVIATIONS Voc Open circuit voltage FF Fill factor Jsc Short circuit density of current PCE Power conversion efficiency Eg Band gap energy PVK Perovskite  Electron affinity ETL Electron transport material Nc Conduction band effective density of states HTL Hole transport material Nv Valence band effective density of states MASnI3 Methylammonium tin tri-iodide r Relative permittivity MAPbI3 Methylammonium lead tri-iodide µn Electron mobility PCBM Phenyl-C61-Butyric-Acid-Methyl- Ester µh Hole mobility PEDOT:PSS poly(3,4-ethylenedioxythiophene) polystyrene sulfonate NA Shallow uniform acceptor density IGZO Indium galium zinc oxide ND Shallow uniform donor density Nt Defect density of states α Absorption coefficient h Plank constant v Frequency of light A and B Material dependent constants mailto:abdelkader-hima@univ-eloued.dz Abdelkader Hima. et al IJECA-ISSN: 2543-3717. June 2020 Page 28 I. Introduction Recently, power conversion efficiency of perovskite solar cells stepped exponentially from 2.2 % in 2006 [1] up to 25.2 % in 2019 [2]. This evolution attracted researcher’s attention to simulate new designs, fabricate perovskite solar cells using deferent methods and study of processing effects on device performances [3-5]. A numerical simulation has been done by researchers they find that the power conversion efficiency is 21.8% under optimized conditions and a PCE of up to 15% were obtained by initially optimizing the preparation of the layer absorbent CH3NH3PbI3 [6]. A study shows that the energy conversion yields of perovskite-based solar cells have improved significantly to over 20 %, which now makes them equivalent to the performance of silicon- based photovoltaics [7, 8]. A group of researchers found that the energy of Auerbach decreases with the rise in the temperature of the treatment giving the lower value of 0.66 eV at 100 ° C, which also corresponds to the best band range of 1 to 49 eV [9]. A numerical study has been made which focuses on the thickness and density of the states (donors and acceptors) and on the efficiency of solar cells. The results found improved the power conversion efficiency (PCE) from 11.73% to 19.58% [9]. The optimization and the thickness of the layers were also done [10, 11]. Most of perovskite solar cells use lead based materials which are not environment-friendly. In this paper, simulation efforts are conducted to study a free lead alternative of perovskite solar cells. Software used for numerical calculation is SCAPS 1D [12, 13]. The objective of our work is to show that the lead-free CH3NH3SnI3 perovskite-based solar cell exhibited better electrical performance when using IGZO material in the ETL. II. Device structure and methodology Figure 1 presents the n-i-p perovskite heterojunction solar cell device that contains three layers: an electron transport layer, a perovskite layer and a hole transport layer. Figure 1. n-i-p solar cell structure The Table 1 summarizes electrical and optical parameters of each layer carefully selected from literature. The solar cell is exposed to a standard AM1.5 solar spectrum under an incident power density of 100 mW/cm 2 . In all simulations, the pre-factor values of A and B (see equation 1.) are taken to be equal to 10 5 and 0 respectively for all used materials for calculation simplicity. α=(A+B/hv).(hv-Eg) 1/2 (1) Where α, h, v, Eg are the absorption coefficient, Plank constant, frequency of light and the band gap respectively, and A and B are model dependent parameters [12]. Table .1. Electrical and optical parameters MASnI3 [3] PEDOT:PSS [3] IGZO [4] PCBM [4] Thickness Variable Variable Variable Variable Eg (eV) 1.9 1.6 3.05 2  (eV) 3.98 3.4 4.16 3.9 r 10 3 10 3.9 Nc (cm-3) 1016 1022 5*1018 2.5*1021 Nv (cm-3) 1015 1022 5*1018 2.5*1021 µn (cm2/Vs) 16.2 4.5*10-4 15 0.02 µh (cm2/Vs) 10.1 9.9*10-5 0.1 0.02 NA (cm -3) 109 1022 - - ND (cm -3) 109 - 1018 2.73*1017 Nt (cm-3) 1014 2.5*1015 1015 1015 Figure 2 presents energy band alignment of different used materials. Abdelkader Hima. et al IJECA-ISSN: 2543-3717. June 2020 Page 29 Figure .2. Energy band alignment III. Result and discussions The first simulated structure is PCBM/MASnI3/PEDOT:PSS/Ag with initial layer thickness of 30 nm, 400 nm and 30 nm respectively, and then we change the PVK layer thickness to find out the one corresponding to the maximum of power conversion efficiency (PCE). In the second simulated structure, we change the ETL material from PCBM to IGZO, and do the same optimization effort to find out the best PVK layer thickness that yields the maximum of PCE. Figure 3 and Figure 4 show the different electrical parameters of both structures in function of PVK layer thickness, where we can notice that the second structure electrical parameters are better than the first structure. We can notice that concerning Voc and FF, the two structures are approximately identical. However, in PCE and Jsc curves, we can notice that in low thickness values the two structures are approximately identical but in high values there is a more difference. Figure .3. Open circuit voltage in function of perovskite layer thickness Figure .4. Short circuit density of current in function of perovskite layer thickness Figure 5 and Figure 6 show the maximum values of the power conversion efficiency which are 12.58 % and 13.12 % for the first structure and the second structure respectively. This PCE optimized value corresponds with the PVK layer thickness of 1 µm. Figure .5. Power conversion efficiency in function of perovskite layer thickness Figure .6. Fill factor in function of perovskite layer thickness Abdelkader Hima. et al IJECA-ISSN: 2543-3717. June 2020 Page 30 Table 2 gives the electrical parameters for both optimized structures (with PVK layer thickness of 1 µm). Table .2. Optimized electrical parameters for both structures Paramater Voc (V) Jsc (mA/cm 2 ) FF (%) PCE (%) 1 st structure 0.75 27 62.25 12.58 2 nd structure 0.75 28.08 62.33 13.12 Figure 7 is presents the IV characteristic of both optimized structures where it is clear that IGZO based structure is better than the PCBM structure. Figure .7. IV characteristics of the 1st and 2nd structures IV. Conclusion In this paper it is found that lead free perovskite CH3NH3SnI3 based solar cell exhibited better electrical performances when using IGZO material as ETL. The PCE of IGZO based structure is better than the PCBM one especially in high perovskite layer thickness. It is found that IGZO based solar cell maximum PCE corresponds with 13.12 % which is better than the PCBM based solar cell maximum PCE of 12.58% with a thickness of 30 nm for both ETL and HTL, and 1 µm for CH3NH3SnI3. Acknowledgements This work is supported by the Research Project University-Formation (PRFU) of Algerian ministry of high education and scientific research (No.A16N01UN390120180002) entitled “Studies on Synthesis, Extraction and Use of Products and Materials for Environment and Energy" References [1] A. Kojima, K. Teshima, T. Miyasaka, and Y. Shirai, "Novel Photoelectrochemical Cell with Mesoscopic Electrodes Sensitized by Lead-Halide Compounds (2) 210th ECS Meeting, Cancun, Mexico", October Abstract, Vol. 397, 2006, pp. 397397 [2] NREL efficiency shart. Available: https://www.nrel.gov/pv/assets/pdfs/best-research-cell- efficiencies. 2020 [3] A. Hima, N. Lakhdar, B. Boubaker, S. Achour, K. Imad, and R. Fatiha, "An optimized perovskite solar cell designs for high conversion efficiency", Superlattices and Microstructures, Vol. 129, 2019, pp. 240-246 [4] N. Lakhdar and A. Hima, "Electron transport material effect on performance of perovskite solar cells based on CH3NH3GeI3", Optical Materials, Vol. 99, 2020, pp. 109517 [5] A. Hima and N. Lakhdar, "Enhancement of efficiency and stability of CH3NH3GeI3 solar cells with CuSbS2", Optical Materials, Vol. 99, 2020, pp. 109607 [6] X. Wei, X. Wang, H. Jiang, Y. Huang, A. Han, Q. Gao, Jiantao Bian, Zhengxin Liu, "Numerical simulation and experimental validation of inverted planar perovskite solar cells based on NiO x hole transport layer", Superlattices and Microstructures, Vol. 112, 2017, pp. 383-393 [7] S. F. Hoefler, G. Trimmel, and T. Rath, "Progress on lead- free metal halide perovskites for photovoltaic applications: a review", Monatsh Chem, Vol. 148, No 5, 2017, pp. 795- 826 [8] M. Konstantakou and T. Stergiopoulos, "A critical review on tin halide perovskite solar cells", Journal of Materials Chemistry A, Vol. 5, No 23, 2017, pp. 11518-11549 [9] I. Kemerchou, F. Rogti, B. Benhaoua, N. Lakhdar, A. Hima, O. Benhaoua, A. Khechekhouche, "Processing Temperature Effect on Optical and Morphological Parameters of Organic Perovskite CH3NH3PbI3 Prepared Using Spray Pyrolysis Method", Journal of Nano- and Electronic Physics; Vol. 11, No 3, 2019, pp. 03011 (4) [10] A. Hima, A. K. Le Khouimes, A. Rezzoug, M. B. Yahkem, A. Khechekhouche, and I. Kemerchou, "Simulation and optimization of CH3NH3PbI3 based inverted planar heterojunction solar cell using SCAPS software", International journal of energetica, Vol. 4, No 1, pp. 56-59 [11] A. Hima, A. Khechekhouche, I. Kemerchou, N. Lakhdar, B. Benhaoua, F. Rogti, I. Telli, A. Saadoun, "GPVDM simulation of layer thickness effect on power conversion efficiency of CH3NH3PbI3 based planar heterojunction solar cell", International Journal of Energetica, Vol. 3, No 1, 2019, pp. 56-59 [12] M. Burgelman, K. Decock, A. Niemegeers, J. Verschraegen, and S. Degrave, "SCAPS manual," ed: February, 2016. [13] M. Burgelman, K. Decock, S. Khelifi, and A. Abass, "Advanced electrical simulation of thin film solar cells", Thin Solid Films, Vol. 535, 2013, pp. 296-301 I. Introduction II. Device structure and methodology III. Result and discussions IV. Conclusion Acknowledgements References