High‑performance transparent p‑CuCoO2/n‑FTO heterostructure photodetector fabricated by co‑sputtering for broadband visible‑light detection

In this work, a transparent p–n heterojunction photodiode based on p-type CuCoO 2 and n-type fluorine-doped tin oxide (FTO) was fabricated using a co-sputtering technique. The structural, optical, morphological, and electrical properties of the CuCoO 2 /FTO heterostructure were systematically analyzed to assess its suitability for optoelectronic photodetection. Rietveld refinement showed that the CuCoO 2 layer possessed a relatively large crystallite size and lower lattice strain compared to the FTO, indicating high crystalline quality. The appearance of Fabry–Perot interference fringes and a slight red shift of the absorption edge confirmed strong interfacial coupling and excellent optical uniformity. FESEM imaging showed compact grains for CuCoO 2 grown on glass and larger aggregated grains when deposited on FTO. Electrical measurements of the p-CuCoO 2 /n-FTO junction demonstrated rectifying behavior, with rectification ratios of 1.8 in the dark and 3.6 under white-light illumination. Extracted diode parameters indicated non-ideal transport influenced by interface states and barrier inhomogeneities, with barrier heights of 0.65 eV (dark) and 0.59 eV (light). Photodetection studies under broadband visible illumination exhibited strong photo-response, achieving a responsivity of 158.2 mA W −1 and detectivity of 1.6 × 10 11 Jones. Overall, the results highlight effective charge separation and demonstrate the promising potential of the CuCoO 2 /FTO heterojunction for high-performance transparent photodetectors.