Design of input couplers for efficient silicon thin film solar absorbers

作者：Kim Sun Kyung^*; Song Kyung Deok; Park Hong Gyu

来源：Optics Express, 2012, 20(23): A997-A1004.

DOI：10.1364/OE.20.00A997

We investigated light absorption in various Si thin film solar absorbers and designed efficient input couplers using finite-difference time-domain simulation. In the simulation, a dielectric coating on Si thin film led to enhanced light absorption at near-ultraviolet to blue wavelengths, while the absorption peaks at longer wavelengths were nearly preserved. In a 300-nm-thick Si film with a 60-nm-thick Si3N4 top-coated layer, current density was augmented by similar to 35% compared to a bare Si film. For broadband absorption, we introduced two-dimensional square-lattice periodic patterns consisting of low-index dielectric materials, SiO2 or Si3N4, or high-index material, Si. The periodic pattern exhibited tunable and pronounced absorption peaks that are indentified as horizontally-propagating waveguide modes. The high absorption peaks were significantly amplified with increasing refractive index of the dielectric pattern. For a Si-patterned structure with a pitch size of 400 nm and a pattern depth of 80 nm, current density was achieved up to 17.0 mA/cm(2), which is enhanced by a factor of 2.1 compared to the current density of bare Si film. Deep understanding of the light absorption in optical cavities with wavelength-scale thickness will be useful in the design of efficient thin film solar absorbers as well as novel nanophotonic elements.

• 出版日期2012-11-5