Photodiode and photodetector characteristics of Ag/MnPc/Si/Ag and Ag/MnPc/SiO2/Ag heterojunctions

Manganese (III) phthalocyanine (4) (modified MnPc) was synthesized by tetramerization of the relevant phthalonitrile under appropriate conditions and thermally coated on Si and SiO2 coated surfaces for the preparation of Ag/MnPc/Si/Ag and Ag/MnPc/SiO2/Ag heterojunctions. Series of investigation methods were applied to assess structural, optical and optoelectronic properties. For the assessment of surface morphology and structure, scanning electron microscopy (SEM) and X-ray diffractometry (XRD) techniques were applied, respectively. Optical properties were evaluated using UV-vis spectrophotometry where energy band gap of the MnPc, Si and SiO2 thin films were derived as 2.46 eV, 2.79 eV and 2.6 eV, respectively. I-V investigation was employed in dark and under various illumination intensities in 20 mW.cm-2, 40 mW.cm-2, 60 mW.cm-2, 80 mW.cm-2 and 100 mW.cm-2. Using I-V data different device parameters like ideality factor, serries resistance and barrier height values were derived. Besides various photodetector and photosensitivity parameters were calculated. It was seen that Ag/MnPc/Si/Ag and Ag/MnPc/SiO2/Ag heterojunctions are sensitive to light but no direct correlation between light intensity and diode parameters were seen.