Near-Infrared Light-Sensitive Hole-Transport-Layer Free Perovskite Solar Cells and Photodetectors with Hexagonal NaYF₄:Yb³⁺,Tm³⁺@SiO₂ Upconversion Nanoprism-Modified TiO₂ Scaffold

Abstract

Hexagonal NaYF4:Yb3+,Tm3+@SiO2 upconversion nanoprism-mixed SiO2 passivation layers are introduced into hole-transport-layer free carbon-based perovskite solar cells to improve the power conversion efficiency. This layer on the top of the TiO2 scaffold has multiple functions: (i) upconversion units could transform near-infrared photons to visible region and thus extend the absorption range; (ii) nanoprisms act as light-scattering centers to prolong light-transmission distance and enhance light harvesting; (iii) SiO2 capping layer could suppress charge recombination at the interface of perovskite/TiO2 through passivation effect. The champion efficiency of our carbon-based device with an optimal amount of upconversion nanoprisms is 14.47%, which is 16.1% higher than that of the reference (12.46%). In addition, our unencapsulated solar cells exhibit good stability against moisture and thermal stressing in ambient condition. We also demonstrated another application of our device as a self-powered photodetector with NIR-sensitive features.