© 2019 IEEE.We present horn-shaped cavities in order to improve the efficiency of energy harvesting in solar cells with traditional materials. Nano-cavities, which are already used for this purpose in the literature, are generally based on the principles of ray optics, while their sizes are in fact comparable to wavelength. Inspired by their effectiveness at radio and microwave frequencies, we design horn-shaped cavities that can effectively trap light and reduce reflections. Based on electromagnetic responses of initial structures, horn geometries are further optimized to minimize reflections and improve absorption efficiency. Numerical results demonstrate excellent performances of the designed cavities, which may even eliminate need for matching layers.