A Comprehensive Analysis of Recombination at Grain Boundaries in High-Efficiency Kesterite-Type Solar Cells

Abstract

The present work reports on microscopic analyses of recombination at grain boundaries (GBs) in polycrystalline Li-doped (Ag,Cu)₂ZnSn(S,Se)₄ (Li-ACZTSSe) and Cu₂ZnSnS₄ (CZTS) absorber layers in high-efficiency solar cells (conversion efficiencies of 14.4% and 10.8%). Recombination velocities s_GB were determined at a large number of GBs by evaluating profiles extracted from cathodoluminescence intensity distributions across GBs in these polycrystalline layers. In both Li-ACZTSSe and CZTS absorber layers, the s_GB values exhibited wide ranges over several orders of magnitude with a median values of 680 and 1100 cm s^–1 for the Li-ACZTSSe and CZTS absorbers. A model that provides a comprehensive explanation for this finding is presented and discussed in detail. Correspondingly, wide ranges for s_GB can be explained by different positive or negative excess charge densities present at different GBs, leading to different downward or upward band bending on the order of several ±10 meV, provided that the net-doping density of the absorber layers is sufficiently large. As a result of the evaluation of the s_GB, input parameters for multidimensional device simulations are obtained. It is revealed that the grain boundary lifetime closely matches the overall effective lifetime, indicating that grain boundary recombination is a key factor limiting the effective carrier lifetime of both Li-ACZTSSe and CZTS absorbers. The estimated V_OC losses due to GBs reach up to 126 mV for Li-ACZTSSe and 88 mV for CZTS. This work highlights that reducing grain boundary recombination via improved passivation and increasing grain size is an effective strategy for achieving further efficiency improvements.

Keywords

cathodoluminescence / grain boundaries / kesterite / recombination velocity / solar cells

References

[1] A. Wang, M. He, M. A. Green, K. Sun, X. Hao, Adv. Energy Mater. 2023, 13, 2203046.

[2] S. Giraldo, Z. Jehl, M. Placidi, V. Izquierdo-Roca, A. Pérez-Rodríguez, E. Saucedo, Adv. Mater. 2019, 31, 1806692.

[3] J. Shi, J. Wang, F. Meng, J. Zhou, X. Xu, K. Yin, L. Lou, M. Jiao, B. Zhang, H. Wu, Y. Luo, D. Li, Q. Meng, Nat. Energy 2024, 9, 1095.

[4] J. Zhou, X. Xu, H. Wu, J. Wang, L. Lou, K. Yin, Y. Gong, J. Shi, Y. Luo, D. Li, H. Xin, Q. Meng, Nat. Energy 2023, 8, 526.

[5] M. A. Green, E. D. Dunlop, M. Yoshita, N. Kopidakis, K. Bothe, G. Siefer, X. Hao, J. Y. Jiang, Prog. Photovolt. Res. Appl. 2025, 33, 3.

[6] Y. Gong, Y. Zhang, E. Jedlicka, R. Giridharagopal, J. A. Clark, W. Yan, C. Niu, R. Qiu, J. Jiang, S. Yu, S. Wu, H. W. Hillhouse, D. S. Ginger, W. Huang, H. Xin, Sci. China Mater. 2021, 64, 52.

[7] Y. Gong, Y. Zhang, Q. Zhu, Y. Zhou, R. Qiu, C. Niu, W. Yan, W. Huang, H. Xin, Energy Environ. Sci. 2021, 14, 2369.

[8] Y. Gong, Q. Zhu, B. Li, S. Wang, B. Duan, L. Lou, C. Xiang, E. Jedlicka, R. Giridharagopal, Y. Zhou, Q. Dai, W. Yan, S. Chen, Q. Meng, H. Xin, Nat. Energy 2022, 7, 966.

[9] Y. Gong, A. Jimenez-Arguijo, A. G. Medaille, S. Moser, A. Basak, R. Scaffidi, R. Carron, D. Flandre, B. Vermang, S. Giraldo, H. Xin, A. Perez-Rodriguez, E. Saucedo, Adv. Funct. Mater. 2024, 34, 2404669.

[10] J. Yang, J. Fu, W. Dong, S. Ren, X. Zhang, J. Su, C. Zhao, M. Wei, D. Zhao, Y. Zhang, S. Wu, Z. Zheng, Energy Environ. Sci. 2024, 17, 9346.

[11] Y. Zhao, X. Chen, S. Chen, Z. Zheng, Z. Su, H. Ma, X. Zhang, G. Liang, Adv. Mater. 2025, 37, 2409327.

[12] N.-J. Hao, R.-X. Ding, C.-J. Tong, K. P. McKenna, J. Appl. Phys. 2023, 133, 145002.

[13] W.-J. Yin, Y. Wu, S.-H. Wei, R. Noufi, M. M. Al-Jassim, Y. Yan, Adv. Energy Mater. 2014, 4, 1300712.

[14] M. Wong, K. Tse, J. Zhu, J. Phys. Chem. C 2018, 122, 7759.

[15] J. Wang, J. Shi, K. Yin, F. Meng, S. Wang, L. Lou, J. Zhou, X. Xu, H. Wu, Y. Luo, D. Li, S. Chen, Q. Meng, Nat. Commun. 2024, 15, 4344.

[16] J. Li, D. B. Mitzi, V. B. Shenoy, ACS Nano 2011, 5, 8613.

[17] T. Thersleff, S. Giraldo, M. Neuschitzer, P. Pistor, E. Saucedo, K. Leifer, Mater. Des. 2017, 122, 102.

[18] J. Cong, M. He, J. S. Jang, J. Huang, K. Privat, Y. Chen, J. Li, L. Yang, M. A. Green, J. H. Kim, J. M. Cairney, X. Hao, Adv. Sci. 2024, 11, 2305938.

[19] M. Ritzer, S. Schönherr, P. Schöppe, W. Wisniewski, S. Giraldo, G. Gurieva, A. Johannes, C. T. Plass, K. Ritter, G. Martínez-Criado, S. Schorr, E. Saucedo, C. Ronning, C. S. Schnohr, ACS Appl. Energy Mater. 2020, 3, 558.

[20] J. Kim, G. Y. Kim, T. T. T. Nguyen, S. Yoon, Y.-K. Kim, S.-Y. Lee, M. Kim, D.-H. Cho, Y.-D. Chung, J.-H. Lee, M.-J. Seong, W. Jo, Phys. Chem. Chem. Phys. 2020, 22, 7597.

[21] S. K. Hwang, S. J. Park, J. H. Park, J. H. Yoon, J. Y. Cho, D. K. Cho, J. Heo, G. Y. Kim, J. Y. Kim, Small 2024, 20, 2307175.

[22] Y. Jian, L. Han, X. Kong, T. Xie, D. Kou, W. Zhou, Z. Zhou, S. Yuan, Y. Meng, Y. Qi, G. Liang, X. Zhang, Z. Zheng, S. Wu, Small Methods 2024, 8, 2400041.

[23] L. Cao, Z. Zhou, W. Zhou, D. Kou, Y. Meng, S. Yuan, Y. Qi, L. Han, Q. Tian, S. Wu, S. Liu (Frank), Small 2024, 20, 2304866.

[24] G. Cui, Y. Yang, L. Bai, R. Wang, Z. Gong, Y. Cao, S. Li, X. Lv, C. Zhu, Small 2024, 20, 2405382.

[25] K. Yin, J. Wang, L. Lou, F. Meng, X. Xu, B. Zhang, M. Jiao, J. Shi, D. Li, H. Wu, Y. Luo, Q. Meng, Nat. Energy 2025, 10, 205.

[26] Y. Qi, N. Wei, Y. Li, D. Kou, W. Zhou, Z. Zhou, Y. Meng, S. Yuan, L. Han, S. Wu, Adv. Funct. Mater. 2024, 34, 2308333.

[27] D.-H. Son, H. K. Park, D.-H. Kim, J.-K. Kang, S.-J. Sung, D.-K. Hwang, J. Lee, D.-H. Jeon, Y. Cho, W. Jo, T. Lee, J. Kim, S.-H. Nam, K.-J. Yang, Carbon Energy 2024, 6, e434.

[28] R. Meng, X. Xu, Y. Huang, L. Wu, J. Li, H. Xu, J. Dong, Y. Liu, X. Fu, H. Guo, G. Wang, Y. Zhang, Mater. Today Phys. 2024, 48, 101580.

[29] H. Xin, S. M. Vorpahl, A. D. Collord, I. L. Braly, A. R. Uhl, B. W. Krueger, D. S. Ginger, H. W. Hillhouse, Phys. Chem. Chem. Phys. 2015, 17, 23859.

[30] J. Li, J. Huang, F. Ma, H. Sun, J. Cong, K. Privat, R. F. Webster, S. Cheong, Y. Yao, R. L. Chin, X. Yuan, M. He, K. Sun, H. Li, Y. Mai, Z. Hameiri, N. J. Ekins-Daukes, R. D. Tilley, T. Unold, M. A. Green, X. Hao, Nat. Energy 2022, 7, 754.

[31] A. Kanevce, M. O. Reese, T. M. Barnes, S. A. Jensen, W. K. Metzger, J. Appl. Phys. 2017, 121, 214506.

[32] M. F. M. Fathil, M. K. M. Arshad, U. Hashim, A. R. Ruslinda, R. M. Ayub, A. H. Azman, M. Nurfaiz, M. Z. M. Kamarudin, M. Aminuddin, A. R. Munir, Proc. IEEE Int. Conf. Semicond. Electron, Kuala Lumpur, Malaysia, 27-29 August 2014 (IEEE, 2014) 2014, pp. 24–27.

[33] B. G. Mendis, L. Bowen, Q. Z. Jiang, Appl. Phys. Lett. 2010, 97, 92112.

[34] J. Quirk, M. Rothmann, W. Li, D. Abou-Ras, K. P. McKenna, Appl. Phys. Rev. 2024, 11, 11308.

[35] D. Abou-Ras, M. Maiberg, Recombination velocities at grain boundaries in solar-cell absorbers – revisited. arXiv. 2025,

[36] J. Y. W. Seto, J. Appl. Phys. 1975, 46, 5247.

[37] M. Krause, A. Nikolaeva, M. Maiberg, P. Jackson, D. Hariskos, W. Witte, J. A. Márquez, S. Levcenko, T. Unold, R. Scheer, D. Abou-Ras, Nat. Commun. 2020, 11, 4189.

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2025 The Author(s). Energy & Environmental Materials published by John Wiley & Sons Australia, Ltd on behalf of Zhengzhou University.