Electrical and Optoelectronic Properties of Chemically Prepared PbS/MnS Heterojunction

Abstract

Lead sulfide (PbS)/manganese sulfide (MnS) heterojunction is synthesized by a simple two-step chemical bath deposition technique. The as-synthesized heterojunction is studied based on the optical and electrical analyses. The optical absorbance spectrum of the test structure confirms dual peaks at two different wavelengths, which has prompted consideration of the two band gaps of the structure. The origin of dual peaks in the absorbance plot is attributed to the existence of the PbS base layer and the MnS window layer. The band gaps are estimated using the conventional Tauc’s method (Eg = 1.75 eV and 2.9 eV) and also by the absorbance spectrum fitting method (Eg = 1.82 eV and 2.97 eV). In the dc analyses, the PbS/MnS heterojunction possesses low dark current and high dynamic resistance. However, under illumination (400–700 nm) a distinct photo-response is observed, showing a substantial rise in device current with the reduction of dynamic resistance. The photo-response of the heterojunction is examined at 635–699 nm, 514–538 nm and 410–452 nm wavelengths by analyzing the photo-current and photo-resistance. The device is found to be more photosensitive at lower wavelength illuminations compared to the higher wavelength exposures.