Tailoring carrier dynamics in inverted mesoporous perovskite solar cells with interface-engineered plasmonics

Compared to extremely high efficiencies achieved by their normal mesoscopic counterparts, significant improvement in those of inverted mesoporous perovskite solar cells (PSCs) has yet to be made. The incorporation of plasmonic nanostructures into mesoporous films has been reported to improve their optoelectronic properties through plasmon resonance effects. Herein, gold nanoparticles coated with a thin layer of a semiconductor (NiOx) are introduced into a mesoporous NiOx layer. Using illumination-dependent characterization, we identify a plasmon-assisted metal-to-semiconductor charge transfer (PACT) mechanism. The hole injection from the Au core into the NiOx shell is not only achieved in the dark due to the ohmic contact nature at the Au@NiOx heterostructure, but also facilitated under illumination due to the plasmon-induced interfacial processes. The charge transfer is observed to substantially downshift the valence band edge and enhance the photoconductivity, as well as favor trap filling of the mesoporous NiOx film, which can lower the effective energy barrier and facilitate hole extraction in PSCs. Consequently, embedding Au@NiOx into the mesoporous layer elevates all of the device parameters simultaneously, with a power conversion efficiency of 20.6% in inverted mesostructured PSCs. These results advance our physical understanding of metal-semiconductor heterostructures and offer additional strategies for manipulating the carrier dynamics of PSCs.