Halide perovskites have emerged as promising materials for optoelectronic devices due to their exceptional optoelectronic properties. These materials have found many applications such as light-emitting diodes, photodetectors, lasers, and solar cells[1–6]. Among them, inorganic halide perovskites CsPb₂Br₅, CsPbBr₃, as well as dual-phase perovskites, are particularly promising. However, achieving the formation of thin films by simple and scalable fabrication methods under ambient conditions with low temperature deposition remains a challenge.

Traditional techniques like spin-coating[1], vapor deposition [7], thermal vacuum deposition [8] or electrospining [9] are difficult to upscale and often require inert atmospheres or high temperatures, limiting their practicality. We address this challenge by developing a simple approach for the fabrication of CsPbBr₃ and CsPb₂Br₅ nanocrystals inks at room temperature, which are then used for the one-step deposition of thin films, using readily available commercial airbrush technology.

This approach offers significant advantages in scalability compared to existing techniques. We demonstrated the deposition of thin films with tunable properties from these nanoinks by a scalable spray-coting process using a simple commercial airbrush under near-ambient conditions. The nanoinks were placed in the airbrush cup, a nitrogen gas flow with a pressure of 0.4 bar was used, and the flow was controlled through nozzle opening. The substrates were heated on a hot plate to allow for instant solvent evaporation.

We investigated the effects of deposition temperature and the number of deposited layers. We observed crystallographic differences with increasing temperature. At room temperature, we obtained phase-pure orthorhombic CsPbBr₃ and tetragonal CsPb₂Br₅. At higher deposition temperatures, traces of PbBr₂ were observed alongside CsPb₂Br₅ using the CsPb₂Br₅ nanoink. Additionally, CsPbBr₃ nanoink deposited at higher temperature exhibited the presence of a dual-phase CsPbBr₃/ CsPb₂Br₅. The optical properties were studied. We noticed similar photoluminescence for all conditions with an emission peak centered around 520 nm characteristic of this perovskite and as has already been noted by others [10-13].

Eventually, we considered the photocurrent properties of the spray-coated films. With optimized deposition parameters, the photoresponse under different lighting conditions (white light and monochromatic light) shows up to four orders of magnitude differences between photocurrent and dark current for dual-phase CsPb₂Br₅/CsPbBr₃ thin films.