It has been nearly 50 years since the idea of an optical rectenna – a device that directly converts free-propagating electromagnetic waves at optical frequencies to direct current – was proposed. Many researchers have worked to realize this idea and overcome the major challenge: coupling an efficient optical antenna to a fast, low-resistance diode. In 2015, we demonstrated for the first time that this challenge could be overcome using carbon nanotubes (CNTs). A metal-insulator-metal diode fabricated at the tip of a vertically aligned CNT has a capacitance on the order of aF and rectifies visible, IR, and solar light into direct current. I will discuss the genesis of this result and the fundamental physics that makes it work. I will highlight results from my group’s current work where we have improved practical device function and increased conversion efficiency substantially in the last 2 years. I will conclude by highlighting remaining challenges and suggesting promising directions for future research.