Over the years, perovskites have attracted much interest due to their potential application in the field of solar cells. Recent advances in the field of perovskites have shown that inorganic cesium lead halide perovskites, among other attractive optical and physical properties, exhibit high thermal stability, which is very important for many technological applications. It is known that the widely used CsPbCl₃ perovskites demonstrate high emission intensity in the blue region, while the replacement of chloride by bromide redshifts the spectrum. Moreover, CsPbX₃ perovskites doped with some lanthanides offer interesting phenomena, such as down-conversion and quantum cutting.

One of such lanthanides is ytterbium (Yb³⁺). Doping with Yb³⁺ is very attractive for achieving quantum cutting phenomenon, which is very attractive for down-conversion of the blue spectral range of solar radiation potentially enabling simple way for boosting efficiency of Si solar cells.  The mechanism of quantum cutting is based on the conversion of one high-energy photon into two low-energy photons, leading to quantum yields of over 100%. The CsPbX₃ matrix is used as an absorbing material for the UV-blue light region, which transfers energy to the Yb³⁺ dopants, increasing the quantum yield. Another important property of Yb³⁺-doped perovskites is their relatively high thermal stability. This means that they can withstand high temperatures without degrading or losing their optical properties, which is essential for use in solar cells.

Perovskite-based materials and electronics are usually fabricated by various techniques, such as solution processing (e.g., spin-coating, blade-coating) or thermal vapor deposition. Unfortunately, aforementioned methods for manufacturing of Yb³⁺-doped perovskites can be very expensive. Luckily, powder grinding (mechanosynthesis) is a low-cost and scalable method that can be performed with water and an annealing temperature as low as 200 °C. These powders are made by incorporating Yb³⁺ ions into the perovskite crystal lattice, improving the optical properties of the material and making it suitable for use in solar cells.

In this work, we present the optical properties of Yb³⁺-doped CsPbX₃ perovskites prepared by mechanosynthesis. The study includes X-ray crystallography (XRD) analysis, absorption and fluorescence spectra, fluorescence lifetime kinetics, and fluorescence quantum yield evaluation. Our findings demonstrate how each step of the powder preparation affects the formation of the perovskite. In addition, the results show that Yb³⁺ ions successfully incorporate into the perovskite lattice and increase the quantum yield when the ratio of Cl^- and Br^- ions in the samples is optimised.