Sustainable optoelectronic architecture of polymer-based HTLs for high-performance CsSnI ₂Br perovskite solar cells

Abstract

Lead-free cesium tin iodide bromide (CsSnI₂Br) perovskite solar cells (PSCs) have emerged as sustainable candidates for next-generation photovoltaics, combining a suitable bandgap with environmental safety. Yet, their performance is hindered by interfacial recombination and the spontaneous oxidation of Sn²⁺ to Sn⁴⁺, which degrades carrier mobility and device stability. While chemical stabilization approaches address this oxidation experimentally, its influence on electronic processes can be systematically evaluated through numerical modeling. In this work, the SCAPS-1D simulator was employed to investigate the optoelectronic response of CsSnI₂Br PSCs integrated with different polymer-based hole transport layers (HTLs), namely PEDOT:PSS, Spiro-OMeTAD, PTAA, Poly-TPD, P3HT, and PANI. Key parameters, including HTL thickness, doping concentration, and defect density -were tuned to analyze charge extraction efficiency and minimize interfacial recombination losses. Among the tested configurations, PEDOT:PSS yielded the highest simulated power conversion efficiency of approximately 21.4%, attributed to its favorable band alignment and enhanced hole mobility. Optimal performance was obtained for an absorber thickness of 0.8 μm and HTL thickness in the 50–80 nm range, provided that bulk and interfacial defect densities were below 5 × 10¹⁴ and 1 × 10¹⁵ cm⁻³, respectively. Additional improvements were achieved with TiO₂ ETL doping levels of 10¹⁷–10¹⁸ cm⁻³ and a back-contact work function near 4.8 eV. The device maintained robust output up to 320 K, demonstrating stable charge transport and reduced trap-mediated losses. These results provide valuable theoretical insights for optimizing HTL selection and interface engineering in efficient, lead-free perovskite photovoltaics.

Keywords

Perovskites solar cells / PEDOT:PSS / CsSnI ₂Br / SCAPS-1D / PSC optoelectronic properties

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

CRediT authorship contribution statement

Wasan J. Kadhem: Writing – review & editing, Writing – original draft, Visualization, Validation, Software, Resources, Methodology, Investigation, Formal analysis, Data curation, Conceptualization. Tariq AlZoubi: Writing – review & editing, Writing – original draft, Visualization, Validation, Supervision, Software, Resources, Project administration, Methodology, Investigation, Funding acquisition, Formal analysis, Data curation, Conceptualization. Mahmoud AlGharram: Writing – review & editing, Visualization, Validation, Methodology, Formal analysis, Data curation. Ghaseb Makhadmeh: Writing – original draft, Validation, Resources, Formal analysis, Data curation. Abdulsalam Abuelsamen: Formal analysis, Data curation. Ahmad M. AL-Diabat: Validation, Data curation. Jestin Mandumpal: Funding acquisition, Formal analysis. Samer H. Zyoud: Formal analysis.

References

[1] F. Zhang, Z. Ma, Z. Shi, X. Chen, D. Wu, X. Li, C. Shan, Recent advances and opportunities of lead-free perovskite nanocrystal for optoelectronic application, Energy Mater. Adv. 2021 (2021) 5198145, doi: 10.34133/2021/5198145.

[2] M. Di Sabatino, R. Hendawi, A.S. Garcia, Silicon solar cells: Trends, manufacturing challenges, and AI perspectives, Crystals 14 (2024) 167, doi: 10.3390/cryst14020167.

[3] T. Al Zoubi, A. Moghrabi, M. Moustafa, S. Yasin, Efficiency boost of CZTS solar cells based on double-absorber architecture: Device modeling and analysis, Sol. Energy 225 (2021) 44-52, doi: 10.1016/j.solener.2021.07.012.

[4] L. Huang, W.R.L. Lambrecht, Electronic band structure, phonons, and exciton binding energies of halide perovskites CsSnCl₃, CsSnBr₃, and CsSnI₃ , Phys. Rev. B 88 (2013) 165203, doi: 10.1103/PhysRevB.88.165203.

[5] P. Zhao, J. Su, Z. Lin, J. Wang, J. Zhang, Y. Hao, X. Ouyang, J. Chang, All-inorganic CsPbI_xBr_3−x perovskite solar cells: Crystal anisotropy effect , Adv. Theory Simul. 3 (2020) 2000055, doi: 10.1002/adts.202000055.

[6] J. Deng, J. Li, Z. Yang, M. Wang, All-inorganic lead halide perovskites: A promising choice for photovoltaics and detectors, J. Mater. Chem. C 7 (2019) 12415-12440, doi: 10.1039/C9TC04164H.

[7] M. Shakil, A. Akram, I. Zeba, R. Ahmad, S.S.A. Gillani, M.A. Gadhi, Effect of mixed halide contents on structural, electronic, optical and elastic properties of CsSnI_3−xBr_x for solar cell applications: First-principles study , Mater. Res. Express 7 (2020) 025513, doi: 10.1088/2053-1591/ab727d.

[8] R. Padmavathy, A. Amudhavalli, R. Rajeswarapalanichamy, K. Iyakutti, Electronic structure and optical properties of CsSnI_3−yBr_y (y = 0, 1, 2, 3) perovskites , Int. J. Mod. Phys. B 33 (2019) 1950003, doi: 10.1142/S0217979219500036.

[9] B. Nakamanya, N. Yu, T. Kakooza, Q. Sun, A. Balilonda, S. Yang, M. Zhu, Stability and performance improvement of cesium tin halide perovskites with astaxanthin treatment, J. Mater. Chem. C 13 (2025) 5209-5220, doi: 10.1039/D4TC04420G.

[10] B. Wu, Y. Zhou, G. Xing, Q. Xu, H.F. Garces, A. Solanki, T.W. Goh, N.P. Padture, T.C. Sum, Long minority-carrier diffusion length and low surface-recombination velocity in inorganic lead-free CsSnI₃ perovskite crystal for solar cells , Adv. Funct. Mater. 27 (2017) 1604818, doi: 10.1002/adfm.201604818.

[11] M. Saliba, T. Matsui, J.Y. Seo, K. Domanski, J.P. Correa-Baena, M.K. Nazeeruddin, S.M. Zakeeruddin, W. Tress, A. Abate, A. Hagfeldt, M. Grätzel, Cesium-containing triple cation perovskite solar cells: Improved stability, reproducibility and high efficiency, Energy Environ. Sci. 9 (2016) 1989-1997, doi: 10.1039/C5EE03874J.

[12] Q. Wang, A. Abate, Strategies toward stable perovskite solar cells, Adv. Mater. Interfaces 5 (2018) 1800264, doi: 10.1002/admi.201800264.

[13] M.H. Li, X. Ma, J. Fu, S. Wang, J. Wu, R. Long, J.S. Hu, Molecularly tailored perovskite/poly(3-hexylthiophene) interfaces for high-performance solar cells, Energy Environ. Sci. 17 (2024) 5513-5520, doi: 10.1039/d4ee02251c.

[14] Md.A. Karim, K. Matsuishi, Md.E. Kayesh, Y. He, A. Islam, Inhibition of Sn²⁺ oxidation in FASnI₃ perovskite precursor solution and enhanced stability of perovskite solar cells by reductive additive , ACS Appl. Mater. Interfaces 15 (2023) 45823-45833, doi: 10.1021/acsami.3c07903.

[15] R. Zhao, N. Wang, Y. Yu, J. Liu, Organoboron polymer for 10% efficiency all-polymer solar cells, Chem. Mater. 32 (2020) 1308-1314, doi: 10.1021/acs.chemmater.9b04997.

[16] S.A. Dar, B.S. Sengar, Design and performance optimization of a novel tri-layer unleaded all inorganic lead-free mixed halide CsSnI_3−xBr_x heterojunction solar cell , Sol. Energy 275 (2024) 112618, doi: 10.1016/j.solener.2024.112618.

[17] N.D. Davlatshoevich, Investigation optical properties of the orthorhombic system CsSnBr_3−xI_x: Application for solar cells and optoelectronic devices , J. Hum. Earth Future 2 (2021) 404-411, doi: 10.28991/HEF-2021-02-04-08.

[18] D.S. Thakur, R.K. Sharma, V. Garg, S. Yadav, DFT-based accurate and efficient bandgap prediction of CsSnI_3−xBr_x and parameter optimization for enhanced perovskite solar cell performance , Phys. B 697 (2025) 416693, doi: 10.1016/j.physb.2024.416693.

[19] M.H. Li, F.Z. Qiu, S. Wang, Y. Jiang, J.S. Hu, Hole transporting materials in inorganic CsPbI_3−xBr_x solar cells: Fundamentals, criteria and opportunities , Mater. Today 52 (2022) 250-268, doi: 10.1016/j.mattod.2021.11.017.

[20] N. Kaur, J. Madan, R. Pandey, Maximizing photovoltaic performance of all-inorganic perovskite CsSnI_3−xBr_x solar cells through bandgap grading and material design , Sol. Energy 274 (2024) 112573, doi: 10.1016/j.solener.2024.112573.

[21] D.D. Nematov, A.S. Burhonzoda, M.A. Khusenov, Kh.T. Kholmurodov, T. Yamamoto, First principles analysis of crystal structure, electronic and optical properties of CsSnI_3−xBr_x perovskite for photoelectric applications , J. Surf. Investig. X-ray Synchrotron Neutron Tech. 15 (2021) 532-536, doi: 10.1134/S1027451021030149.

[22] F. Alshaeer, M.A. Mohammed, M. Zorah, N. Alharbi, H.M.A. Mahmoud, A.M.E. Ahmed, B.A. Mohammed, G. Abdulkareem-Alsultan, M.F. Nassar, Synergistic defect passivation and charge transport enhancement via thiosemicarbazide-functionalized carbon nanotubes for high-efficiency lead-free CsSnI₃ perovskite solar cells: A pathway to 23.34% efficiency , J. Alloys Compd. 1026 (2025) 180428, doi: 10.1016/j.jallcom.2025.180428.

[23] J. Liu, S. Wang, W. Zhu, Z. Tang, L. Ding, F. Hao, Highly symmetric Lewis base coordinated with Sn²⁺ for reducing voltage loss and retarding oxidation in tin-halide perovskite solar cells , Chem. Eng. J. 453 (2023) 139975, doi: 10.1016/j.cej.2022.139975.

[24] D. Jones, Y. An, J. Hidalgo, C. Evans, J.N. Vagott, J.P. Correa-Baena, Polymers and interfacial modifiers for durable perovskite solar cells: A review, J. Mater. Chem. C 9 (2021) 12509-12522, doi: 10.1039/D1TC01243F.

[25] Y. Ma, J. Ge, A.K.Y. Jen, J. You, S. Liu, Polymer boosts high performance perovskite solar cells: A review, Adv. Opt. Mater. 12 (2024) 2301623, doi: 10.1002/adom.202301623.

[26] J. Bing, J. Kim, M. Zhang, J. Zheng, D.S. Lee, Y. Cho, X. Deng, C.F.J. Lau, Y. Li, M.A. Green, S. Huang, A.W.Y. Ho-Baillie, The impact of a dynamic two-step solution process on film formation of Cs_0.15(MA_0.7FA_0.3)_0.85PbI₃ perovskite and solar cell performance , Small 15 (2019) 1804858, doi: 10.1002/smll.201804858.

[27] D.J. Fairfield, H. Sai, A. Narayanan, J.V. Passarelli, M. Chen, J. Palasz, L.C. Palmer, M.R. Wasielewski, S.I. Stupp, Structure and chemical stability in perovskite-polymer hybrid photovoltaic materials, J. Mater. Chem. A 7 (2019) 1687-1699, doi: 10.1039/C8TA07545J.

[28] S. Wang, X.Y. Gong, M.X. Li, M.H. Li, J.S. Hu, Polymers for perovskite solar cells, JACS Au 4 (2024) 3400-3412, doi: 10.1021/jacsau.4c00615.

[29] S. Wang, H. Yao, W. Zhu, C. Wu, Z. Tang, J. Liu, L. Ding, F. Hao, Stabilization of perovskite lattice and suppression of Sn²⁺/Sn⁴⁺ oxidation via formamidine acetate for high efficiency tin perovskite solar cells , Adv. Funct. Mater. 33 (2023) 2215041, doi: 10.1002/adfm.202215041.

[30] L. Chen, H. Cai, X. Luo, X. Zhao, S. Wu, Modifying the buried PEDOT:PSS/perovskite interface by dual-functional material to optimize the performance of pure Sn-based perovskite solar cells, Surf. Interfaces 57 (2025) 105743, doi: 10.1016/j.surfin.2025.105743.

[31] M.T. Dang, L. Hirsch, G. Wantz, P3HT:PCBM, best seller in polymer photovoltaic research, Adv. Mater. 23 (2011) 3597-3602, doi: 10.1002/adma.201100792.

[32] M.H. Li, X. Gong, S. Wang, L. Li, J. Fu, J. Wu, Z.A. Tan, J.S. Hu, Facile hydrogen-bonding assisted crystallization modulation for large-area high-quality CsPbI₂Br films and efficient solar cells , Angew. Chem. Int. Ed. 136 (2024) e202318591, doi: 10.1002/anie.202318591.

[33] M. Burgelman, P. Nollet, S. Degrave, Modelling polycrystalline semiconductor solar cells, Thin Solid Films 361-362 (2000) 527-532, doi: 10.1016/S0040-6090(99)00825-1.

[34] M. Burgelman, K. Decock, S. Khelifi, A. Abass, Advanced electrical simulation of thin film solar cells, Thin Solid Films 535 (2013) 296-301, doi: 10.1016/j.tsf.2012.10.032.

[35] T. Al Zoubi, B. Mourched, M. Al Gharram, G. Makhadmeh, O. Abu Noqta, Improving photovoltaic performance of hybrid organic-inorganic MAGeI₃ perovskite solar cells via numerical optimization of carrier transport materials (HTLs/ETLs) , Nanomaterials 13 (2023) 2221, doi: 10.3390/nano13152221.

[36] M. Moustafa, T. Al Zoubi, S. Yasin, Numerical analysis of the role of p-MoSe₂ interfacial layer in CZTSe thin-film solar cells using SCAPS simulation , Optik 247 (2021) 167885, doi: 10.1016/j.ijleo.2021.167885.

[37] S. Yasin, Z.A. Waar, T. Al Zoubi, M. Moustafa, High efficiency performance of eco-friendly C₂N/FASnI₃ double-absorber solar cell probed by numerical analysis , Opt. Mater. 122 (2021) 111743, doi: 10.1016/j.optmat.2021.111743.

[38] S. Yasin, Z.A. Waar, T. Al Zoubi, M. Moustafa, Optoelectronic simulation of a high efficiency C₂N based solar cell via buffer layer optimization , Opt. Mater. 119 (2021) 111364, doi: 10.1016/j.optmat.2021.111364.

[39] M. Moustafa, T. Alzoubi, Numerical study of CdTe solar cells with p-MoTe₂ TMDC as an interfacial layer using SCAPS , Mod. Phys. Lett. B 32 (2018) 1850269, doi: 10.1142/S021798491850269X.

[40] M. Moustafa, T. Al Zoubi, S. Yasin, Optoelectronics simulation of CIGS-based solar cells using a Cd-free nontoxic ZrS_xSe_2−x as a novel buffer layer , Braz. J. Phys. 52 (2022) 1-10, doi: 10.1007/s13538-022-01146-z.

[41] T. Al Zoubi, M. Al-Gharram, M. Moustafa, Insights into the impact of defect states and temperature on the performance of kesterite-based thin-film solar cells, Optik 264 (2022) 169442, doi: 10.1016/j.ijleo.2022.169442.

[42] M. Benyoucef, T. Alzoubi, J.P. Reithmaier, M. Wu, A. Trampert, Nanostructured hybrid material based on highly mismatched III-V nanocrystals fully embedded in silicon, Phys. Status Solidi A 211 (2014) 817-822, doi: 10.1002/pssa.201330395.

[43] T. Al Zoubi, W.J. Kadhem, M. Al Gharram, G. Makhadmeh, M.A.O. Abdelfattah, A. Abuelsamen, A.M. AL-Diabat, O. Abu Noqta, B. Lazarevic, S.H. Zyoud, B. Mourched, Advanced optoelectronic modeling and optimization of HTL-free FASnI₃/C60 perovskite solar cell architecture for superior performance , Nanomaterials 14 (2024) 1062, doi: 10.3390/nano14121062.

[44] S. Li, Y.L. Cao, W.H. Li, Z.S. Bo, A brief review of hole transporting materials commonly used in perovskite solar cells, Rare Met. 40 (2021) 2712-2729, doi: 10.1007/s12598-020-01691-z.

[45] R. Sen, M. Yadav, An investigation on organic and inorganic materials for hole transport layer in lead-free third-generation solar cell, J. Opt. 52 (2023) 672-682, doi: 10.1007/s12596-022-01027-3.

[46] Y. Wang, L. Duan, M. Zhang, Z. Hameiri, X. Liu, Y. Bai, X. Hao, PTAA as efficient hole transport materials in perovskite solar cells: A review, Sol. RRL 6 (2022) 2200234, doi: 10.1002/solr.202200234.

[47] N. Rono, A.E. Merad, J.K. Kibet, B.S. Martincigh, V.O. Nyamori, Optimization of hole transport layer materials for a lead-free perovskite solar cell based on formamidinium tin iodide, Energy Technol. 9 (2021) 2100859, doi: 10.1002/ente.202100859.

[48] Q.Y. Chang, Y.D. An, H.M. Cao, Y.Z. Pan, L.Y. Zhao, Y.L. Chen, Y. We, S.W. Tsang, H.L. Yip, L.C. Sun, Z. Yu, Precursor engineering enables high-performance all-inorganic CsPbIBr₂ perovskite solar cells with a record efficiency approaching 13% , J. Energy Chem. 90 (2024) 16-22, doi: 10.1016/j.jechem.2023.10.021.

[49] A.S. Chouhan, N.P. Jasti, S. Avasthi, Effect of interface defect density on performance of perovskite solar cell: Correlation of simulation and experiment, Mater. Lett. 221 (2018) 150-153, doi: 10.1016/j.matlet.2018.03.095.

[50] R. Ma, J. Yu, T. Liu, G. Zhang, Y. Xiao, Z. Luo, G. Chai, Y. Chen, Q. Fan, W. Su, G. Li, E. Wang, X. Lu, F. Gao, H. Yan, B. Tang, All-polymer solar cells with over 16% efficiency and enhanced stability enabled by compatible solvent and polymer additives, Aggregate 3 (2022) e58, doi: 10.1002/agt2.58.

[51] H. Zhang, X. Qiao, Y. Shen, M. Wang, Effect of temperature on the efficiency of organometallic perovskite solar cells, J. Energy Chem. 24 (2015) 729-735, doi: 10.1016/j.jechem.2015.10.007.

[52] G. Zhang, L. Wang, C. Zhao, Y. Wang, R. Hu, J. Che, S. He, W. Chen, L. Cao, Z. Luo, M. Qiu, S. Li, G. Zhang, Efficient all-polymer solar cells enabled by interface engineering, Polymers 14 (2022) 3835, doi: 10.3390/polym14183835.

[53] V. Srivastava, S.H. Reddy, B. Anitha, A.G.M. Namboothiry, A comparative study of defect density of states for single, mixed and bulk heterojunction perovskite solar cells, AIP Conf. Proc. 2082 (2019) 050013, doi: 10.1063/1.5093873.

[54] N.A. Tukadiya, Z.D. Ponkiya, N. Joshi, D. Upadhyay, P.K. Jha, Machine learning and SCAPS-1D based prediction and validation of RbGeBr₃ perovskite solar cell , Sol. Energy 300 (2025) 113760, doi: 10.1016/j.solener.2025.113760.

[55] G. Pindolia, S.M. Shinde, P.K. Jha, Non-leaded, KSnI₃ based perovskite solar cell: A DFT study along with SCAPS simulation , Mater. Chem. Phys. 297 (2023) 127426, doi: 10.1016/j.matchemphys.2023.127426.

[56] M. Benyoucef, M. Usman, T. Alzoubi, J.P. Reithmaier, Pre-patterned silicon substrates for the growth of III-V nanostructures, Phys. Status Solidi A 209 (2012) 2402-2410, doi: 10.1002/pssa.201228367.

[57] T. Al Zoubi, M. Al-Gharram, G. Makhadmeh, O. Abu Noqta, Comparative analysis of optoelectronic and structural characteristics in electrochemically synthesized hybrid-nanocomposites based on PANI-CSA/metal oxide nanoparticles, Phys. B 713 (2025) 417380, doi: 10.1016/j.physb.2025.417380.

[58] V.H. Diniz Araújo, A.F. Nogueira, J.C. Tristão, L.J. dos Santos, Fullerene-C60 and PCBM as interlayers in regular and inverted lead-free PSCs using CH₃NH₃SnI₃: An analysis of device performance and defect density dependence by SCAPS-1D , RSC Adv. 14 (2024) 10930-10941, doi: 10.1039/D4RA00634H.

[59] I.M. Dharmadasa, J.D. Bunning, A.P. Samantilleke, T. Shen, Effects of multi-defects at metal/semiconductor interfaces on electrical properties and their influence on stability and lifetime of thin film solar cells, Sol. Energy Mater. Sol. Cells 86 (2005) 373-384, doi: 10.1016/j.solmat.2004.08.009.

[60] X. Chen, J. Cheng, L. He, L. Zhao, C. Zhang, A. Pang, J. Li, Hole transport materials for tin-based perovskite solar cells: Properties, progress, prospects, Molecules 28 (2023) 3787, doi: 10.3390/molecules28093787.

[61] C.H. Kuan, G.S. Luo, S. Narra, S. Maity, H. Hiramatsu, Y.W. Tsai, J.M. Lin, C.H. Hou, J.J. Shyue, E.W.G. Diau, How can a hydrophobic polymer PTAA serve as a hole-transport layer for an inverted tin perovskite solar cell? Chem. Eng. J. 450 (2022) 138037, doi: 10.1016/j.cej.2022.138037.

[62] S.W. Park, J.H. Heo, H.J. Lee, H. Kim, S. Kim, S.H. Im, Compositional design for high-efficiency all-inorganic tin halide perovskite solar cells, ACS Energy Lett. 8 (2023) 5061-5069, doi: 10.1021/acsenergylett.3c02032.

[63] K. Nishimura, D. Hirotani, M.A. Kamarudin, Q. Shen, T. Toyoda, S. Iikubo, T. Minemoto, K. Yoshino, S. Hayase, Relationship between lattice strain and efficiency for Sn-perovskite solar cells, ACS Appl. Mater. Interfaces 11 (2019) 31105-31110, doi: 10.1021/acsami.9b09564.