Tunable plasmon-enhanced broadband light harvesting for perovskite solar cells

In this work, we report a reliable method for synthesizing (Au, Au/Ag core)/(TiO₂ shell) nanostructures with their plasmonic wavelengths covering the visible light region for perovskite solar cells. The mono- and bi-metallic core-shell nanoparticles exhibit tunable localized surface plasmon resonance wavelength and function as “light tentacle” to improve the photo-electricity conversion efficiency. Plasmonic nanoparticles with different sizes and shapes, different thicknesses of TiO₂ shell and Ag interlayer are found to have a strong influence on the localized surface plasmon resonance enhancement effect. The experimental photovoltaic performance of perovskite solar cells is significantly enhanced when the plasmonic nanoparticles are embedded inmesoporous TiO₂ scaffolds. A champion photo-electricity conversion efficiency of 17.85% is achieved with nanoparticles (Au/Ag, λ_LSPR = 650 nm), giving a 18.7% enhancement over that of the pristine device (15.04%). Finite-difference time-domain simulations show that nanorod Au in mesoporus TiO₂ scaffold induces the most intense electromagnetic coupling, and provides a novel emitter for photon flux in mesoporous perovskite solar cells. These theoretical results are consistent with the corresponding experimental those. Thus, enhancing the incident light intensities around 650 nm will be most favorable to the improvement of the photo-electricity conversion efficiency of perovskite solar cells.