Ultrahigh omnidirectional, broadband, and polarization-independent optical absorption over the visible wavelengths by effective dispersion engineering

Achieving perfect light absorption at a subwavelength-scale thickness has various advantageous in terms of cost, flexibility, weight, and performance for many different applications. However, obtaining perfect absorbers covering a wide range of wavelengths regardless of incident angle and input polarization without a complicated patterning process while maintaining a small thickness remains a challenge. In this paper, we demonstrate flat, lithography-free, ultrahigh omnidirectional, polarization-independent, broadband absorbers through effective dispersion engineering. The proposed absorbers show day-integrated solar energy absorption up to 96%, which is 32% better than with lossy semiconductor/metal absorbers. The proposed simple yet effective method can be applied to light absorption thin film structures based on various types of highly lossy semiconductor materials, including emerging 2D materials.