Long life light

The ability of ‘glow-in-the-dark’ materials to slowly release energy as light over extended periods of time is used in several contexts, from emergency signage to optical imaging. Most of these materials make use of rare inorganic elements and require extreme processing conditions during fabrication. Ryota Kabe and Chihaya Adachi offer a different solution. They use the power of chemistry to control the excitation properties of organic molecules—which are already harnessed to great effect in the field of organic light-emitting diodes—and show how a blend of two simple molecules can be engineered to slowly release their stored energy as light over times spanning seconds to hours. Stability issues remain to be resolved (perhaps by encapsulation), but the transparent, soluble, flexible and colour-tunable nature of these new materials is attractive for a range of applications.