Ag@SiO₂ Core-shell Nanoparticles Embedded in a TiO₂ Mesoporous Layer Substantially Improve the Performance of Perovskite Solar Cells

In this study, Ag@SiO₂ nanoparticles were synthesized by a modified Stöber method for preparing the TiO₂ mesoporous layer of carbon counter electrode-based perovskite solar cells (PSCs) without a hole transporting layer. Compared with normal PSCs (without Ag@SiO₂ incorporated in the TiO₂ mesoporous layer), PSCs with an optimal content of Ag@SiO₂ (0.3 wt. % Ag@SiO₂-TiO₂) show a 19.46% increase in their power conversion efficiency, from 12.23% to 14.61%, which is mainly attributed to the 13.89% enhancement of the short-circuit current density, from 20.23 mA/cm² to 23.04 mA/cm². These enhancements mainly contributed to the localized surface Plasmon resonance effect and the strong scattering effect of Ag@SiO₂ nanoparticles. However, increasing the Ag@SiO₂ concentration in the mesoporous layer past the optimum level cannot further increase the short-circuit current density and incident photon-to-electron conversion efficiency of the devices, which is primarily ascribed to the electron transport pathways being impeded by the insulating silica shells inside the TiO₂ network.