Tailored Au@TiO2 nanostructures for the plasmonic effect in planar perovskite solar cells

Among the various methods to advance solar cell technologies, the implementation of nanoparticles with plasmonic effects is an effective way to make better use of incident light and manage carrier dynamics. Herein, for the first time we report the systematic synthesis of gold nanospheres or nanorods coated with a thin layer of titanium oxide (Au@TiO2) and use them to examine the plasmonic effect in planar heterojunction perovskite solar cells. The most efficient assembly mode is to embed the Au@TiO2 nanorods into the electron transport layer (ETL), which elevates the average power conversion efficiency (PCE) from 15.76% to 16.35%, mainly attributed to the short-circuit current enhancement. The optimized device assembled with Au@TiO2 nanorods delivers an efficiency of 20.10%. We further explored the plasmonic enhancement effect of Au@TiO2 nanorods based on the combination of UV-visible absorption spectroscopy, incident photon-to-current efficiency (IPCE), photoluminescence (PL) and transient photocurrent decay (TPC). The results indicate better charge separation/transfer as well as facilitated carrier transport in the presence of plasmonic particles. This work provides an insightful understanding of plasmonic effects in planar perovskite solar cells and also presents a promising approach for simultaneous photon and electron management.