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A back contact interface in a kesterite Cu2ZnSn(S,Se)4 (CZTSSe) photovoltaic device plays an important role in fabricating high quality semiconducting photoactive layers and improving carrier extraction efficiency. However, uncontrolled decomposition reactions between the CZTSSe absorber layer and Mo electrode result in high series resistance and recombination at the back interface. The insertion of high work function MoO3 as an interfacial layer is considered as a promising way to engineer the back contact. This highlights the importance of elucidating the chemistry and dynamics of MoO3 at the Mo/kesterite interface in the CZTSSe annealing process. Herein, A detailed investigation of the elemental diffusion and chemistry of the back contact with the MoO3 intermediate layer during selenization is carried out. The results demonstrate that the presence of the MoO3 interfacial layer largely suppresses the chemical reaction between Mo and CZTSSe in the annealing process, inducing high quality CZTSSe absorbing films with fewer voids and reducing the thickness of MoSe2 from 209 to 84 nm when the optimized thickness of MoO3 is 10 nm. This finally leads to the increase in device efficiency from 9.02% to 10.92%, and the best performance where an efficiency of 11.37% is achieved. [ABSTRACT FROM AUTHOR]

Interface passivation is a key method for improving the efficiency of perovskite solar cells, and 2D/3D perovskite heterojunction is the mainstream passivation strategy. However, the passivation layer also produces a new interface between 2D perovskite and fullerene (C 60 ), and the properties of this interface have received little attention before. Here, the underlying properties of the 2D perovskite/C 60 interface by taking the 2D TEA 2 PbX 4 (TEA = C 6 H 10 NS; X = I, Br, Cl) passivator as an example are systematically expounded. It is found that the 2D perovskite preferentially exhibits (002) orientation with the outermost surface featuring an oriented arrangement of TEACl, where the thiophene groups face outward. The outward thiophene groups further form a strong π-π stacking system with C 60 molecule, strengthening the interaction force with C 60 and facilitating the creation of a superior interface. Based on the vacuum-assisted blade coating, wide-bandgap (WBG, 1.77 eV) perovskite solar cells achieved impressive records of 19.28% (0.09 cm 2 ) and 18.08% (1.0 cm 2 ) inefficiency, respectively. This research not only provides a new understanding of interface processing for future perovskite solar cells but also lays a solid foundation for realizing efficient large-area devices., (© 2024 Wiley‐VCH GmbH.)