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oai:recercat.cat:2117/4490752026-02-09T09:14:17Zcom_2072_1033col_2072_452950

Enhancing the performance of cu2zngese4 solar cells with metallic and transparent back electrodes via lithium doping Errafyg, Abdeljalil Ennouhi, Naoufal Anefnaf, Ikram Aazou, Safae Rotaru, Victoria Tiwari, Kunal Jiménez Arguijo, Alex Perez Rodriguez, Alejandro Guc, Maxim Saucedo Silva, Edgardo Ademar Sekkat, Zouheir Universitat Politècnica de Catalunya. Departament d'Enginyeria Electrònica Universitat Politècnica de Catalunya. MNT-Solar - Grup de Micro i Nano Tecnologies per Energia Solar Àrees temàtiques de la UPC::Energies::Energia solar fotovoltaica::Cèl·lules solars Tandem solar cell Kesterite Postdeposition treatment C-silicon Lithium doping Crystalline silicon (c-Si) solar cells have nearly reached their theoretical efficiency limits, constrained by the intrinsic properties of silicon. To overcome these limitations, tandem solar cell devices combining a narrow-bandgap c-Si bottom cell with a wide-bandgap top cell have emerged as a promising approach. Ge-based kesterite materials (Cu2ZnGe(SS)e4), offer significant potential for this application due to their tunable optoelectronic properties, earth-abundant composition, and compatibility with cost-effective fabrication techniques. However, improving the structural and electronic properties of Ge-kesterite absorbers remains critical for advancing their performance. Lithium (Li) doping, previously successful in Sn-based kesterite materials (Cu2ZnSnSSe4), provides an approach to enhance crystallinity, defect passivation, and grain growth in Ge-kesterite materials. This study investigates the effect of lithium doping on the structural, morphological, and optoelectronic properties of Cu2ZnGe(SS)e4 (CZGSe) absorbers prepared using sputtered metallic precursors. Lithium was introduced via a Lithium fluoride (LiF) nano-layer, with an optimal thickness of 10 nm significantly improving absorber quality. Doped CZGSe solar cells achieved an efficiency of 6.4% on Mo substrates, demonstrating enhanced crystallinity, grain growth, and Voc compared to undoped samples. Applying this doping strategy to transparent back electrodes showed notable material improvements, but slightly lower efficiency compared to Mo-based cells. These findings underscore the potential of lithium as a promising alkali dopant for Ge-kesterite materials, paving the way for their integration into tandem and next-generation photovoltaic devices. Postprint (published version) 2025-12-01 Article Errafyg, A. [et al.]. Enhancing the performance of cu2zngese4 solar cells with metallic and transparent back electrodes via lithium doping. «Scientific reports», 1 Desembre 2025, vol. 15, núm. article 34625. 2045-2322 https://hdl.handle.net/2117/449075 10.1038/s41598-025-18247-9 eng https://www.nature.com/articles/s41598-025-18247-9 http://creativecommons.org/licenses/by-nc-nd/4.0/ Open Access Attribution-NonCommercial-NoDerivatives 4.0 International application/pdf Springer