Highly Efficient Infrared Light-Converting Perovskite Solar Cells: Direct Electron Injection from NaYF₄:Yb³⁺, Er³⁺ to the TiO₂

Organic-inorganic hybrid perovskite solar cells (PSCs) exhibit high photovoltaic performance, while their utilization of infrared and near-infrared (NIR) irradiation is poor. The up-conversion material can highly convert the NIR into visible light, providing the PSCs with a possibility of utilizing NIR. In this report, the critical TiO₂ mesoporous layer was successfully improved with the incorporation of 30 nm cubic NaYF₄:Yb³⁺, Er³⁺ up-conversion nanoparticles (UCNPs). Transmission electron microscopy and fluorescence spectrum analysis of the mesoporous layer confirmed the formation of the shared interface between TiO₂ and UCNPs. The NaYF₄:Yb³⁺, Er³⁺ nanoparticles can convert the 980 nm NIR into 520, 545, and 660 nm emissions, in which the excited electrons at 520 and 545 nm can directly inject into the conduction band of TiO₂ by shared interfaces. Meanwhile, the visible light (660 nm) can be absorbed by perovskite layer. At last, the device not only enhanced the short-circuit current but also exhibited a high power conversion efficiency.