CsPbBr₃ has attracted significant attention for high-performance optoelectronic applications, including X-ray detection, owing to its high-Z composition, excellent charge transport properties and intrinsic defect tolerance.[1] It is particularly promising as an absorber in low-cost, high-sensitivity direct X-ray detectors, where it can outperform current market standards limited by poor X-ray absorption or expensive processing.[2] However, fabricating micrometre-thick, pinhole-free films with controlled crystallinity by scalable methods remains challenging, as solution processing of thick layers often leads to inhomogeneous crystallization, pinholes and high defect densities.

In this poster, I will present the growth of phase-pure CsPbBr₃ films using a custom-built dual-zone chemical vapor deposition (CVD) system. This solvent-free approach requires a stoichiometric vapor phase despite the different volatilities of CsBr and PbBr₂. By tuning the precursor ratio, reaction time and substrate position within the temperature gradient, secondary phases such as CsPb₂Br₅ and Cs₄PbBr₆ are suppressed, yielding ~3 µm-thick films with grains up to 35 µm, an order of magnitude larger than in spin-coated films. I will also discuss the influence of the substrate: films grown on fused silica are smoother, larger-grained and show a lower Urbach energy than those on soda-lime glass, which we attribute to its chemically inert surface and to substrate-dependent strain.

Compared with spin-coated references, the CVD films show strongly prolonged photoluminescence decays, extending up to ~3 µs versus ~40 ns. Terahertz photoconductivity measurements reveal a Drude-like response and a nearly twofold higher carrier mobility (~365 versus ~171 cm² V⁻¹ s⁻¹), indicating reduced carrier localization at grain boundaries.

To evaluate their practical applicability, proof-of-concept lateral photodetectors were fabricated on fused silica. These devices exhibit dark currents below the instrumental detection limit at 0 V and switching ratios up to ~9 × 10⁴, together with a responsivity of 0.176 A W⁻¹, a specific detectivity of 8.4 × 10¹² Jones and a noise current of 3.2 × 10⁻¹³ A Hz⁻¹ᐟ² at 100 Hz. The devices remain stable under repeated switching and continuous bias, and their crystal structure is unchanged after one year of unencapsulated ambient storage. Under X-ray irradiation, the sensitivity increases with film thickness and reaches 7.51 µC Gy⁻¹ cm⁻² at low dose rates. These findings link CVD growth conditions to microstructure, charge transport and device performance, and position CVD-grown CsPbBr₃ as a promising platform for stable, low-noise photodetectors and X-ray sensors.[3]