Thin-film thermoelectric generators with ball lenses which transmittance the visible light

Abstract

We designed and fabricated thin-film thermoelectric generators (TEGs) with ball lenses on a glass substrate that transmit the visible solar light and convert the near-infrared (NIR) solar light to electric energy. In the calculation, the ball lenses separated the visible light and the NIR light using the chromatic aberration to defocus the NIR light and to focus the visible light onto the glass substrates. The NIR light was irradiated onto the hot sides of pn junctions on the glass substrate. The visible light was transmitted the glass substrate to use as daylight through the pin hole in the center of the TEGs. The torus-shaped TEGs which composed of serially connected pn junctions were designed using ray tracing method. The outer and inner diameters of the TEG were 1000 μm and 52 μm, respectively. The TE thin-film elements (p-type: Bi_0.5Sb_1.5Te₃, n-type: Bi₂Te_2.7Se_0.3) were formed using lithography and radio-frequency magnetron sputtering. The generation properties and the open-circuit voltage and the maximum generation power were 0.076 mV/pair and 0.018 nW/pair, respectively when the solar light was irradiated at 298K.