First-Principles Investigation of Structural Stability and Optoelectronic Properties of Lead-Free CsSnₓGe₁₋ₓI₃ Mixed-Halide Perovskites for Advanced Optoelectronic Applications

Authors

  • Samuel Adebayo
    Ladoke Akintola University of Technology, Ogbomoso
  • Ajide Adeolu Bamidele
  • Mojoyinola Kofoworola Awodele
    Ladoke Akintola University of Technology image/svg+xml
  • Ayodeji Oladiran Awodugba
    Ladoke Akintola University of Technology image/svg+xml

Keywords:

CsSnₓGe₁₋ₓI₃, Lead-free halide perovskites, Density Functional Theory (DFT), Structural stability, Electronic properties, Optical absorption, Band structure, Density of states (DOS)

Abstract

The escalating demand for sustainable energy solutions necessitates the development of high performance, environmentally benign photovoltaic materials. Lead-halide perovskites, while highly efficient, present significant toxicity concerns, driving intensive research into lead-free alternatives. This study employs first-principles density functional theory (DFT) to comprehensively investigate the thermodynamic stability, phase behavior, and optoelectronic characteristics of the mixed-cation lead-free perovskite series, CsSnₓGe₁₋ₓI₃. Our objective was to elucidate the fundamental properties governing their suitability for next-generation solar cells and optoelectronic devices.

Key findings reveal that the solid solutions of CsSnₓGe₁₋ₓI₃ exhibit enhanced thermodynamic favourability and stability compared to their single-metal counterparts, highlighting the critical role of compositional engineering. Specifically, CsSn₀.₅Ge₀.₅I₃ demonstrates optimal thermodynamic stability, underscoring the beneficial impact of tin incorporation. Electronic structure analysis indicates a tunable direct electronic bandgap, ranging from 1.331 eV for CsSnI₃ to 1.927 eV for CsGeI₃, with a linear compositional dependence, making these materials highly adaptable for various spectral absorptions. A notable phase transition and subsequent phase segregation are observed when tin doping exceeds x = 0.53, leading to compositions such as CsSn₁/₃Ge₂/₃I₃ and CsSn₀.₇₅Ge₀.₂₅I₃, which possess favorable bandgaps and high absorption coefficients. Furthermore, detailed evaluation of optical properties, including the complex refractive index and absorption coefficient, confirms exceptional light-harvesting potential across the visible and near-infrared regions.

These theoretical insights provide a robust foundation for the rational design and synthesis of stable, efficient, and eco-friendly halide perovskites. The demonstrated tunability of optoelectronic properties and intrinsic thermodynamic stability positions CsSnₓGe₁₋ₓI₃ as a promising candidate for advanced photovoltaic and light-emitting diode applications, thereby contributing significantly to the advancement of sustainable nanotechnology in energy conversion.

Dimensions

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Samuel Adebayo, Yetunde Ajayeoba, Ibraheem Ayobami Oladosu, Adekunle Kazeem Dauda, Victoria Olaide Adenigba, Akintunde Festus Ojeniyi, Adegbenro Sunday Ajani, Olusola Akinrinola, George Atilade Alagbe, Mojoyinola Kofoworola Awodele, Oluwaseun Adedokun and, Ayodeji Oladiran Awodugba, A Narrative Review of CsSnGeI3 (Caesium Tin Germanium Iodide) Perovskite Material, Synthesis, Characterization, and Applications in Optoelectronics and Photovoltaics (2026), https://doi.org/10.56201/rjpst.vol.9.no3.2026.pg47.78

Published

2026-07-24

How to Cite

First-Principles Investigation of Structural Stability and Optoelectronic Properties of Lead-Free CsSnₓGe₁₋ₓI₃ Mixed-Halide Perovskites for Advanced Optoelectronic Applications (S. Adebayo, A. A. Bamidele, M. K. Awodele, & A. O. Awodugba, Trans.). (2026). Nigerian Journal of Applied Physics, 2(2), 160-168. https://doi.org/10.62292/

Issue

Vol. 2 No. 2 (2026): Nigerian Journal of Applied Physics - Vol. 2 No. 2

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Articles
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Copyright (c) 2026 Samuel Adebayo, Ajide Adeolu Bamidele, Mojoyinola Kofoworola Awodele, Ayodeji Oladiran Awodugba

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This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.

How to Cite

First-Principles Investigation of Structural Stability and Optoelectronic Properties of Lead-Free CsSnₓGe₁₋ₓI₃ Mixed-Halide Perovskites for Advanced Optoelectronic Applications (S. Adebayo, A. A. Bamidele, M. K. Awodele, & A. O. Awodugba, Trans.). (2026). Nigerian Journal of Applied Physics, 2(2), 160-168. https://doi.org/10.62292/