Tailoring carrier dynamics in perovskite solar cells via precise dimension and architecture control and interfacial positioning of plasmonic nanoparticles

Abstract

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 (J_sc). 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 (V_oc). Taken together, the PSCs constructed by employing a sandwich-like TiO₂/Au NPs/TiO₂ ETL exhibit both greatly enhanced J_sc and V_oc, 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.