Structural, morphological, and optical properties of Sr-doped CuO thin films: Experimental and first-principles analysis

We investigate the structural, electronic, and optical properties of Sr-doped CuO thin films, using both experimental techniques and density functional theory methods. X-ray diffraction, Raman spectroscopy, and electron microscopy confirmed the presence of a monoclinic CuO phase (C2/c) with high crystallinity, optimal at 4 % Sr doping. However, at doping levels of 6 % or higher, defect formation and reduced crystallinity were observed. Optical analysis indicated a reduction in bandgap and increased structural disorder with higher doping. DFT calculations showed that pure CuO has a direct bandgap of 1.36 eV, increasing to between 1.4 and 1.54 eV with Sr incorporation. The material exhibited anisotropic optical behavior, with strong conductivity, absorption, and reflectivity peaks attributed to band-to-band transitions. The absorption spectra demonstrated excellent visible light performance. Importantly, experimental and theoretical bandgap values showed strong agreement, validating the computational approach. These results highlight the tunable optoelectronic properties of Sr-doped CuO for solar energy and photonic applications.