Engineering High-Performance CIGS Solar Cells: Structural Design and Process Development

Abstract

The development of high-efficiency copper indium gallium diselenide (CIGS) solar cells is currently driven by a dual strategy of internal structural refinement and integration into multi-junction tandem architectures. This study aims to systematically analyze the key design and optimization strategies required to overcome the 33.7% Shockley-Queisser limit of single-junction devices. The results demonstrate that bandgap engineering, particularly through double-graded “notch” profiles, significantly enhances charge carrier collection and improves overall device performance, while alkali metal post-deposition treatments effectively reduce interface recombination losses. Furthermore, integrating CIGS with perovskite top cells in two-terminal (2T) and four-terminal (4T) configurations is a promising pathway to achieving efficiencies exceeding 30%. By combining advanced vacuum-based fabrication techniques, such as the three-stage co-evaporation process, with precise optical management, CIGS technology is positioned as a versatile candidate for both high-performance terrestrial and radiation-tolerant space applications.

Keywords

CIGS solar cells / Bandgap engineering / Buffer layer optimization / Tandem solar cells / CIGS photovoltaics / Interface engineering

Statement of the Use of Generative AI and AI-Assisted Technologies in the Writing Process

During the preparation of this manuscript, the authors used ChatGPT (OpenAI) to assist with language editing and refinement. After using this tool, the authors carefully reviewed and edited the content and take full responsibility for the content of the published article.

Author Contributions

Conceptualization, A.K.; Methodology, D.I.; Software, D.I.; Validation, D.I. and A.K.; Formal Analysis, D.I.; Investigation, D.I.; Resources, A.K.; Data Curation, D.I.; Writing—Original Draft Preparation, D.I.; Writing—Review & Editing, D.I. and A.K.; Visualization, D.I.; Supervision, A.K.; Project Administration, A.K.

Ethics Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

No new data were created or analyzed in this study. Data sharing is not applicable.

Funding

This research received no external funding.

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.

References

[1] Amrillah T, Rizki IN, Alviani VN. From binary to quaternary copper chalcogenide compounds in solar cells technology: Recent progress and perspectives. Sol. Energy 2025, 299, 113784. DOI:10.1016/j.solener.2025.113784

[2] Lee S, Lee ES, Kim TY, Cho JS, Eo YJ, Yun JH, et al. Effect of annealing treatment on CdS/CIGS thin film solar cells depending on different CdS deposition temperatures. Sol. Energy Mater. Sol. Cells 2015, 141, 299-308. DOI:10.1016/j.solmat.2015.05.052

[3] Komilov A. Gallium content-dependent efficiency limits of CIGS solar cells at AM1.5G solar irradiance. J. Photonics Energy 2021, 11, 035501. DOI:10.1117/1.jpe.11.035501

[4] Chi W, Banerjee SK. Comparison and integration of CuInGaSe and perovskite solar cells. J. Energy Chem. 2023, 78, 463-475. DOI:10.1016/j.jechem.2022.12.039

[5] Salhi B. The Photovoltaic Cell Based on CIGS: Principles and Technologies. Materials 2022, 15, 1908. DOI:10.3390/ma15051908

[6] Sivasankar SM, Amorim CDO, Cunha AFD. Progress in Thin-Film Photovoltaics: A Review of Key Strategies to Enhance the Efficiency of CIGS, CdTe, and CZTSSe Solar Cells. J. Compos. Sci. 2025, 9, 143. DOI:10.3390/jcs9030143

[7] Lv X, Zheng Z, Zhao M, Wang H, Zhuang D. Investigation on Preparation and Performance of High Ga CIGS Absorbers and Their Solar Cells. Materials 2023, 16, 2806. DOI:10.3390/ma16072806

[8] Jafari SMH, Orouji AA, Abbasi A. Numerical investigation of ultrathin CIGS solar cells featuring SiO₂/GaAs double rear passivation. Sci. Rep. 2026, 16, 4549. DOI:10.1038/s41598-025-34707-8

[9] Wu Z, Tao S, Jia M, Han J, Zhou J, Baranova M, et al. Bandgap Engineering of CIGS: Active Control of Composition Gradient. Energies 2025, 18, 6089. DOI:10.3390/en18236089

[10] Mohamad Noh MF, Arzaee NA, Fat CC, Sieh Kiong T, Mat Teridi MA, Mahmood Zuhdi AW. Perovskite/CIGS tandem solar cells: Progressive advances from technical perspectives. Mater. Today Energy 2024, 39, 101473. DOI:10.1016/j.mtener.2023.101473

[11] Kumar V, Prasad R, Chaure NB, Singh UP. Advancement in Copper Indium Gallium Diselenide (CIGS)-Based Thin-Film Solar Cells. In Recent Advances in Thin Film Photovoltaics; Springer: Singapore, 2022. DOI:10.1007/978-981-19-3724-8_2

[12] Petrova-Koch V, Hezel R, Goetzberger A. High-Efficient Low Cost Photovoltaics; Saule Chapter; Springer: Cham, Switzerland, 2009. DOI:10.1007/978-3-030-22864-4

[13] Sinha S, Nandi DK, Pawar PS, Kim SH, Heo J. A review on atomic layer deposited buffer layers for Cu(In,Ga)Se₂ (CIGS) thin film solar cells: Past, present, and future. Sol. Energy 2020, 209, 515-537. DOI:10.1016/j.solener.2020.09.022

[14] Ramanujam J, Singh UP. Copper indium gallium selenide based solar cells—A review. Energy Environ. Sci. 2017, 10, 1306-1319. DOI:10.1039/c7ee00826k

[15] Han A, Zhang Y, Song W, Li B, Liu W, Sun Y. Structure, morphology and properties of thinned Cu(In,Ga)Se₂ films and solar cells. Semicond. Sci. Technol. 2012, 27, 035022. DOI:10.1088/0268-1242/27/3/035022

[16] Ishizuka S, Yamada A, Fons P, Niki S. Texture and morphology variations in (In,Ga)₂Se₃ and Cu(In,Ga)Se₂ thin films grown with various Se source conditions. Prog. Photovolt. Res. Appl. 2013, 21, 544-553. DOI:10.1002/pip.1227

[17] Su CY, Ho WH, Lin HC, Nieh CY, Liang SC. The effects of the morphology on the CIGS thin films prepared by CuInGa single precursor. Sol. Energy Mater. Sol. Cells 2011, 95, 261-263. DOI:10.1016/j.solmat.2010.04.072

[18] Komilov AG, Nasrullaev YZ. Influence of the Environment on the Parameters of CIGS-Based Photovoltaic and Photovoltaic-Thermal Converters Used in Real Conditions. Appl. Sol. Energy 2021, 57, 8-12. DOI:10.3103/S0003701X21010047

[19] Lin L, Ravindra NM. Temperature dependence of CIGS and perovskite solar cell performance: An overview. SN Appl. Sci. 2020, 2, 1361. DOI:10.1007/s42452-020-3169-2

[20] Alarifi IM. Advanced selection materials in solar cell efficiency and their properties—A comprehensive review. Mater. Today Proc. 2021, 81, 403-414. DOI:10.1016/j.matpr.2021.03.427

[21] Lin L, Ravindra NM. CIGS and perovskite solar cells—An overview. Emerg. Mater. Res. 2020, 9, 812-824. DOI:10.1680/jemmr.20.00124

[22] Li H, Qu F, Luo H, Niu X, Chen J, Zhang Y, et al. Engineering CIGS grains qualities to achieve high efficiency in ultrathin Cu(In_xGa_1-x)Se₂ solar cells with a single-gradient band gap profile. Results Phys. 2019, 12, 704-711. DOI:10.1016/j.rinp.2018.12.043

[23] Machkih K, Oubaki R, Makha M. A Review of CIGS Thin Film Semiconductor Deposition via Sputtering and Thermal Evaporation for Solar Cell Applications. Coatings 2024, 14, 1088. DOI:10.3390/coatings14091088

[24] Movla H. Optimization of the CIGS based thin film solar cells: Numerical simulation and analysis. Optik 2014, 125, 67-70. DOI:10.1016/j.ijleo.2013.06.034

[25] Sun X, Silverman T, Garris R, Deline C, Alam MA. An Illumination-and Temperature-Dependent Analytical Model for Copper Indium Gallium Diselenide (CIGS) Solar Cells. IEEE J. Photovolt. 2016, 6, 1298-1307. DOI:10.1109/JPHOTOV.2016.2583790

[26] Rahman MF, Hasan MK, Chowdhury M, Islam MR, Rahman MH, Rahman MA, et al. A qualitative Design and optimization of CIGS-based Solar Cells with Sn2S3 Back Surface Field: A plan for achieving 21.83% efficiency. Heliyon 2023, 9, e22866. DOI:10.1016/j.heliyon.2023.e22866

[27] Chirilǎ A, Reinhard P, Pianezzi F, Bloesch P, Uhl AR, Fella C, et al. Potassium-induced surface modification of Cu(In,Ga)Se₂ thin films for high-efficiency solar cells. Nat. Mater. 2013, 12, 1107-1111. DOI:10.1038/nmat3789

[28] Minemoto T, Matsui T, Takakura H, Hamakawa Y, Negami T, Hashimoto Y, et al. Theoretical analysis of the effect of conduction band offset of window/CIS layers on performance of CIS solar cells using device simulation. Sol. Energy Mater. Sol. Cells 2001, 67, 83-88. DOI:10.1016/S0927-0248(00)00266-X

[29] Siebentritt S. Alternative buffers for chalcopyrite solar cells. Sol. Energy 2004, 77, 767-775. DOI:10.1016/j.solener.2004.06.018

[30] Platzer-Björkman C, Lu J, Kessler J, Stolt L. Interface study of CuInSe₂/ZnO and Cu(In,Ga)Se₂/ZnO devices using ALD ZnO buffer layers. Thin Solid Films 2003, 431-432, 321-325. DOI:10.1016/S0040-6090(03)00229-3

[31] Stephan C. Structural Trends in off Stoichiometric Chalcopyrite Type Compound Semiconductors. Ph.D. Thesis, Freien Universität Berlin, Berlin, Germany, 2011. DOI:10.5442/d0011

[32] Intal D, Ebong AU. Thin-film solar photovoltaics: Trends and future directions. Renew. Sustain. Energy Rev. 2026, 226, 116464. DOI:10.1016/j.rser.2025.116464

[33] Mohammadi R, Hayati M, Shama F. High-efficiency monolithic CIGS/CIGS tandem solar cell with WS2 buffer layers. Micro Nanostruct. 2026, 213, 208589. DOI:10.1016/j.micrna.2026.208589