A solar material that soaks up light strongly — and loses its charges about 75% more slowly

Solar materials face a frustrating trade-off: the ones that absorb sunlight most strongly also tend to lose the electrical charges that sunlight creates before those charges can be collected as power. Researchers led by the University of Oxford, working with Wuhan University, have found a way around it in a material called bismuth sulfide. When light hits it, the freed charges can slip into a nearby, slightly lower energy level that acts like a quiet waiting room — they stay there, safe from being lost, while the material keeps absorbing light just as strongly. Using flashes of laser light lasting less than a billionth of a second, the team measured the effect: at room temperature, charges were lost about 75% more slowly than in conventional materials that absorb light as strongly. This is not a new efficiency record for a finished panel, and the finding, published in Nature, was shown in thin films in a laboratory. Its real value is as a design rule: other materials with the same energy-level arrangement could be hunted down on purpose, instead of found by luck.

SDG 7 · Affordable and clean energy — Mechanism: tech innovation