Placing plasmonic nanoparticles (NPs) in close proximity to semiconductor nanostructures renders effective tuning of the optoelectronic properties of semiconductors through the localized surface plasmon resonance (LSPR)-induced enhancement of light absorption and/or promotion of carrier transport. Herein, we report on, for the first time, the scrutiny of carrier dynamics of perovskite solar cells (PSCs) via sandwiching monodisperse plasmonic/dielectric core/shell NPs with systematically varied dielectric shell thickness yet fixed plasmonic core diameter within an electron transport layer (ETL). Specifically, a set of Au NPs with precisely controlled dimensions (i.e., fixed Au core diameter and tunable SiO2 shell thickness) and architectures (plain Au NPs and plasmonic/dielectric Au/SiO2 core/shell NPs) are first crafted by capitalizing on the star-like block copolymer nanoreactor strategy. Subsequently, these monodisperse NPs are sandwiched between the two consecutive TiO2 ETLs. Intriguingly, there exists a critical dielectric SiO2 shell thickness, below which hot electrons from the Au core are readily injected to TiO2 (i.e., hot electron transfer (HET)); this promotes local electron mobility in the TiO2 ETL, leading to improved charge transport and increased short-circuit current density (Jsc). It is also notable that the HET effect moves up the Fermi level of TiO2, resulting in an enhanced built-in potential and open-circuit voltage (Voc). Taken together, the PSCs constructed by employing a sandwich-like TiO2/Au NPs/TiO2 ETL exhibit both greatly enhanced Jsc and Voc, delivering champion PCEs of 18.81% and 19.42% in planar and mesostructured PSCs, respectively. As such, the judicious positioning of rationally designed monodisperse plasmonic NPs in the ETL affords effective tailoring of carrier dynamics, thereby providing a unique platform for developing high-performance PSCs.
