Effect of CuPc Film Thickness Prepared by Thermal Evaporation on the Performance of an Optical Detector

Copper phthalocyanine (CuPc) is a semiconductor that is chemically very stable, highly optically absorbing of visible light, and possesses good charge transport properties, so it is a promising material for optoelectronic devices and photodetectors. In this study, CuPc thin films with thickness range 146.4–632.4 nm were grown on ultrasonically cleaned glass substrates by thermal evaporation at a pressure of 2.2 × 10-5 torr. Structure, morphology, and optical properties were analyzed to study the effect of thickness on photoconductive response. X-ray diffraction analysis revealed that the films were polycrystalline monoclinic with preferred (312) orientation. AFM images showed increase in grain size with thickness, and roughness decreased at higher thicknesses due to increased surface density. Absorption spectra showed distinct Q and B regions, and the energy gap was observed to increase from 1.60 to 2.92 eV with increased thickness. Dark and illumination current–voltage curves showed Schottky-type behavior, indicating the existence of a potential barrier across the metal–semiconductor junction that is responsible for the charge transport. The photodetector device made from CuPc thin films also exhibited a good optical response with a quantum efficiency (η ) value of 10.89%, responsivity (R) value of 0.054 A/W, and specific responsivity (D*) value of 109 Jones when illuminated with 625 nm. These findings corroborate that CuPc films exhibit thickness-dependent optical and electrical characteristics and are good prospects for stable high-performance Schottky-type photodetector applications.