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Over 15% efficient wide-band-gap Cu(In,Ga)S2 solar cell: Suppressing bulk and interface recombination through composition engineering

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The progress of Cu(In,Ga)S2 remains significantly limited mainly due to photovoltage (Voc) losses in the bulk and at the interfaces. Here, via a combination of photoluminescence, cathodoluminescence, electrical measurements, and ab initio modeling, we address the bulk and interface losses to improve ~ 1.6 eV bandgap (Eg) Cu(In,Ga)S2. The optoelectronic quality of the absorber improves upon reducing the [Cu]/[Ga+In] (CGI) ratio, as manifested by the suppression of deep defects, higher quasi-Fermi level splitting (QFLS), improved charge carrier lifetime, and higher Voc. We identify antisite CuIn/CuGa as a major performance-limiting deep defect by comparing the formation energies of various intrinsic defects. Interface recombination is suppressed using a Zn(O,S) buffer layer in Cu-poor devices, which leads to the activation energy of recombination equal to the Eg. We demonstrate efficiency of 15.2% with Voc of 902 mV from a H2S-free, Cd-free, and KCN-free process.



40 Engineering, 4016 Materials Engineering, 7 Affordable and Clean Energy

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Elsevier BV
Engineering and Physical Sciences Research Council (EP/R025193/1)
EPSRC (EP/V029231/1)
The authors acknowledge Dr. Nathalie Valle and Dr. Brahime El Adib, Luxembourg Institute for Science and Technology (LIST), for SIMS measurement. Mohit and Damilola gratefully acknowledge partial funding of this research through the Luxembourgish Fond National de la Recherche FNR through the MASSENA project (FNR PRIDE/15/10935404). CL studies were supported by the EPSRC under grant number EP/R025193/1. Dr. Christian Monachon of Attolight is thanked for his ongoing support of the CL system. Diana Dahliah was financially supported by the Conseil de l’Action Internationale (CAI) through a doctorate grant ‘‘Coopération au Développment’’. We acknowledge access to various computational resources: the Tier-1 supercomputer of the Fédération Wallonie-Bruxelles funded by the Walloon Region (grant agreement no. 1117545), and all the facilities provided by the Université catholique de Louvain (CISM/UCL) and by the Consortium des Equipements de Calcul Intensif en Fédération WallonieBruxelles (CECI).