NOVELTY - A perpetual thermal energy harvester comprises substrate, buffer layer attached on the substrate (100) in which the buffer layer (117) comprises similar material system or dissimilar material system from the substrate, primary electrode (150), secondary electrode (155), absorption layer (115) electrically connected between the primary and secondary electrodes, and insulator layer (145) attached on the absorption layer which is opposite surface from the substrate. The absorption layer comprises primary material (120), secondary material (130) and tertiary material (135).    USE - Perpetual thermal energy harvester e.g. photovoltaic device as continuous power device for generating power from infrared spectrum.    ADVANTAGE - The power is efficiently generated using perpetual thermal energy harvester during both day and night times.    DETAILED DESCRIPTION - A perpetual thermal energy harvester comprises substrate, buffer layer attached on the substrate in which the buffer layer comprises similar material system or dissimilar material system from the substrate, primary electrode, secondary electrode, absorption layer electrically connected between the primary and secondary electrodes, and insulator layer attached on the absorption layer which is opposite surface from the substrate. The absorption layer comprises primary material, secondary material and tertiary material. The materials in the absorption layer comprises planar two or more p-n or p-i-n junctions in series which increases the open circuit voltage, and two or more planar p-n or p-i-n junctions comprising cutoff wavelength between 2-40 mm.    DESCRIPTION OF DRAWING(S) - The drawing shows a cross-sectional view of the thermal energy harvester.    Substrate (100)    Antireflective coating (110)    Absorption layer (115)    Buffer layer (117)    Primary material (120)    Secondary material (130)    Tertiary material (135)    Insulator layer (145)    Primary electrode (150)    Secondary electrode (155)