Zimmermann, L.; Petrulevicius, J.; Menzel, D.; Bernardes de Araujo, W.M.; Morita, K.; Maniyarasu, S.; Simmonds, M.; Salimi, Y.; Kim, D. K.; Mathies, F.; Scheler, F.; Berwig, S.; Sung, W.; Nihonyanagi, S.; Mahboubi Soufiani, A.; Harter, A.; Jankauskas, V.; Kurpiers, J.; Malinauskas, T.; Tahara, T.; Creatore, M.; Wood, S.; Schlatmann, R.; Stannowski, B.; Korte, L.; Köhnen, E.; Getautis, V.; Albrecht, S.: A novel carborane-based electron transport material for high-performance perovskite/silicon tandem solar cells. Energy & Environmental Science 19 (2026), p. 4734-4746
10.1039/d6ee01246a
Open Access Version
Abstract:
The fullerene C60 is the prevalent electron transport material (ETM) in high-efficiency perovskite/silicon tandem solar cells. However, it introduces intrinsic limitations, including high interfacial non-radiative recombination losses, the formation of mechanically weak interfaces, and high parasitic absorption. Here, we report a non-fullerene ETM based on a meta-carborane core and 9-fluorenylidene malononitrile functional groups (mCB-FMN) that addresses these challenges while maintaining the processing advantages of C60. Thermally evaporated mCB-FMN forms uniform, conformal thin films that enable efficient electron extraction and strongly suppress interfacial non-radiative recombination losses compared to C60. The introduction of this novel ETM further reduces oxygen-induced degradation of the perovskite/ETM interface, improves the nucleation of the SnOx buffer layer grown by atomic layer deposition and enhances interfacial adhesion within the perovskite/ETM/SnOx stack. Its wide optical bandgap is another key advantage, as it minimizes parasitic absorption losses in tandem solar cells. Replacing C60 with mCB-FMN in opaque p?i?n perovskite single-junction devices improves the power conversion efficiency (PCE) by 1.5% (absolute), driven by a 110 meV increase in open-circuit voltage (VOC). Proof-of-concept perovskite/silicon tandem integration of mCB-FMN yields a PCE of 31.3%, surpassing the C60-based reference by 2.4% (absolute) through simultaneous improvements in VOC and short-circuit current density. These results establish mCB-FMN as a novel non-fullerene ETM for perovskite/silicon tandem solar cells that overcomes the performance limitations of conventional C60 and highlight carborane-based compounds as a promising new class of materials for high-efficiency perovskite photovoltaics.