Highly Efficient Perovskite Photovoltaics Enabled by Molecular Bridging at the SnO₂/Perovskite Interface

The contact at the interface of the perovskite and the electron transport layer is critical in determining the efficiency and durability of perovskite solar cells (PSCs). The nonuniformity of the carrier significantly influences the carrier transport mechanisms at the buried interface. In order to tackle this issue, a bridging molecule, (2-aminoethyl)phosphonic acid (AEP), is utilized for the modulation of the tin oxide (SnO₂)/perovskite buried interface in a typical PSC. The phosphonic acid group forms a strong interaction with SnO₂, which effectively suppresses photocarrier traps and leakage current while also tuning the surface potential. In addition, the amino group plays a significant role in the perovskite film. Subsequently, a single-light-harvesting material structure based on FTO/SnO₂/AEP/(MA_0.85FA_0.15)Pb(I_0.85Cl_0.15)₃/Spiro-OMeTAD/Au PSCs is designed. Highly efficient PSCs have been developed through the selective integration of a mixed-cation perovskite material, featuring a band gap of 1.5 eV. The performance of AEP-modified PSCs was calculated and analyzed using the solar cell capacitor simulator program. Simulating the AEP-modified PSCs yields optimal device configurations, achieving a short-circuit current density of 26.65 mA/cm², a fill factor of 87.34%, and an open-circuit voltage of 1.21 V. Furthermore, a comparison between the parameters of the AEP-free PSC and the optimized device revealed that the addition of an interfacial AEP passivation layer could increase the power conversion efficiency from 19.65 to 28.36%, resulting in an improved photon-to-electron conversion property.