Noticeably enhanced opto-electrical and photodetection performance of spray pyrolysis grown Mn:CdS nanostructured thin films for visible-light sensor applications

Mn:CdS nanostructured thin films with improved optoelectronic performance were grown on glass substrates via spray pyrolysis method with different Mn doping concentrations. The structural properties of the films were analyzed using X-ray diffraction (XRD) patterns which revealed that the grown films exhibit hexagonal wurtzite structure with a growth oriented along (002) plane. A systematic effect of Mn doping was observed on the structural and optical properties of the films. The grown films were found to be optically active and show high absorbance in the visible region. The optical band gap values of the films obtained from the absorbance spectra are in the range of 2.33-2.42 eV. A composition dependent analysis of Raman spectra of the thin films shows that the crystalline quality of as grown films is high. The near band, edge (NBE) and the defect related emission were recorded using photoluminescence spectroscopy with different excitation sources. Photodetector devices fabricated based on Mn:CdS thin films and their performance analysis show improved visible light photodetection with the incorporation of Mn in the CdS system. The film doped with 3.0 wt.% Mn concentrations demonstrates high photoresponse parameters such as photosensitivity (∼ 402), responsivity (8.37 A/W), detectivity (1.45 × 1012 Jones) and external quantum efficiency (EQE∼1954%) with 0.3 s and 0.6 s rise and decay times, respectively, in comparison with 1.0 and 5.0 wt.% Mn doped films. This study demonstrates that the 3.0 wt.% Mn doping concentration is the optimal for CdS based visible light photo-detector applications via cost effective method.