CeO6Te2 nanosheets for multifunctional broadband visible light photodetection and NLO applications: an experimental and computational approach

Abstract

CeO₆Te₂ (COT) nanosheets (NS) were synthesized via a hydrothermal route with systematically varied Ce : Te ratios (1 : 1, 1 : 2, 1 : 3), yielding phase-pure, highly crystalline samples and were systematically characterized to correlate their structural, optical, and nonlinear properties. The structural characteristics by X-ray diffraction (XRD), Raman, and X-ray photoelectron spectroscopy (XPS) analyses confirmed the formation of a layered monoclinic phase with improved crystallinity. Morphological characterization revealed well-formed 2D NS with enhanced crystallinity and atomic ordering at higher Te content. Optical studies by UV–Vis diffuse reflectance spectra (DRS) demonstrated progressive bandgap narrowing (1.84–1.67 eV) attributed to Te–O hybridization and lattice modifications. The red-shifting of photoluminescence peaks is caused by Te-induced structural and electronic modifications. Photodetector devices (PDs) exhibited pronounced and stable photoresponse, with COT-2 showing the highest photosensitivity (264.5%) and detectivity (1.38 × 10⁷ Jones), while COT-3 displayed maximal photocurrent and nonlinear optical (NLO) coefficients (|χ⁽³⁾| ≈ 62.6 × 10⁻³ esu). Temporal I–T analysis revealed fast and stable switching, and Z-scan studies confirmed robust third-order nonlinearity dominated by saturable absorption and self-focusing. Density functional theory (DFT) calculations corroborated the indirect band structure and predicted robust optical activity. These results establish CeO₆Te₂ as a promising multifunctional material for broadband photodetection, optical switching, and nonlinear photonic device applications, with performance tunable via the Ce : Te ratio.