Previous studies have revealed that single-walled carbon nanotubes (SWCNTs) strongly absorb light, especially in the near-infrared region, and convert it into heat. There even has been a report that fluffy SWCNTs can burst into flames when exposed to a camera flash, which means the local temperature has reached 600-700C. This effect has already been used to develop effective CNT-based cancer killers or extremely dark materials. In a new twist, researchers in China have now discovered that SWCNT buckypapers have a large Seebeck coefficient, indicating a strong capability to convert heat into electricity. Based on this, they have designed an opto-electronic power source which converts the incident light into electricity. While this has been discussed as a theoretical mechanism, the team at Tsinghua University in Beijing has actually fabricated an integrated device that outputs a macroscopic voltage, moving forward towards practical applications.