Preparation of NaYF[sub.4]:Tm, Yb, and Gd Luminescent Nanorods/SiO[sub.2] Nanospheres Composite Thin Film and Its Application in Perovskite Solar Cells

In this study, we aim to minimize light loss and achieve high power conversion efficiencies (PCE) in perovskite solar cells (PSCs) by employing a spectral conversion film component with antireflection properties. In our scheme, NaYF[sub.4]:Tm, Yb, and Gd luminescent nanorod/silica nanosphere-based thin films are applied on CH[sub.3]NH[sub.3]PbI[sub.3] PSCs to improve the device efficiency. The film was fabricated by spin coating an aged silica sol containing NaYF[sub.4]:Tm, Yb, and Gd luminescent nanorods. The size and the spectral conversion properties of the NaYF[sub.4]:Tm, Yb, and Gd luminescent nanorods were controlled by tuning the Gd[sup.3+] ion concentration. The microstructure and the transmittance properties of the thin film were controlled by changing the concentration of NaYF[sub.4]:Tm, Yb, and Gd luminescent nanorod in silica sol. The thin films have excellent spectral conversion properties while exhibiting a maximum transmittance. The photovoltaic performance of PSCs with NaYF[sub.4]:Tm, Yb, and Gd luminescent nanorod/silica nanosphere-based thin films was systematically investigated. The light transmittance was optimized to 95.1% on a cleaned glass substrate, which resulted in an average increase of about 3.0% across the broadband range of 400–800 nm. The optimized films widen the spectrum of light absorbed by conventional PSC cells and reduce reflections across a broad range, enhancing the photovoltaic performance of PSCs. As a result, the PCE of the PSC increased from 14.51% for the reference device without a thin film to 15.67% for the PSC device with an optimized thin film. This study presents a comprehensive solution to the problem of Fresnel reflection and spectral response mismatch of the PSCs, which provides new ideas for the light management of PSCs.