systems and methods for an improved solar / infrared conversion efficiency using multiple rectennas , one for each band of the spectrum . each rectenna is optimally efficient for each spectrum band . an antenna receives at least one of a visible or infrared spectrum . rectifying circuits coupled to the antenna generate a current based on a portion of the spectrum received by the at least one antenna . each rectenna operates efficiently using a different operating voltage . the operating voltages are based on the selected load resistor and the current - voltage characteristics for the diode of the rectifying circuit at the associated spectrum portion .