Metamaterials‐Based Photoelectric Conversion: From Microwave to Optical Range

Photoelectric conversion (PC) is an essential process for the devices based on the utilization of electrical signals, such as solar cells, sensors, imaging, and communication. As an emerging research field, great advances are made in the PC devices based on the metamaterials (MMs) hitherto. The MMs exhibit unique electromagnetic resonance properties, which can be used for perfect absorbers and are promising for efficient PC from microwave to optical range, though the absorption mechanism varies with the waveband. Perfect absorption in the microwave is mainly induced by the electromagnetic polariton resonance, and surface plasmon resonance (SPR) becomes dominant as the frequency approaches to optical band. Thus, the MMs-based photoelectric devices are realized via an electronic approach in the microwave band, and are based on the SPR-induced hot carriers in the optical band. Since terahertz wave falls between the microwave and optical band, terahertz photoelectric devices exhibit unique characteristic different from the electronics and optics, while still bear similarity to both of them, which is dependent on the frequency. Hence, this review covers major advances in the aspects of fundamentals and engineering for the MMs-based photoelectric devices from microwave to optical range.