PbTe thin films on CdZnTe(111) substrates were epitaxially grown by Molecular Beam Epitaxy. Prototype photovoltaic mid-IR detectors were fabricated using ZnS thin films as insulated materials, In2O3 as transparent conductive thin films, and metallic In thin films as the Ohmic contact electrodes. The wavelength response of the detectors covers the range from 1.5 μm to 5.5 μm at 77 K, and the detectivity is higher than 2×1010 cm·Hz1/2W-1. The peak detectivity D*λ calculated using R0A data reaches 4.35×1010 cm·Hz1/2W-1 at 77 K. The cut-off wavelength blue shifts and the detectivity decreases as the measurement temperatures rise. The main factors that influence the detectivity and R0A parameters are discussed.