A new kind of solar panel has achieved 9% efficiency in converting water into hydrogen and oxygen–mimicking a crucial step in natural photosynthesis. Outdoors, it represents a major leap in the technology, nearly 10 times more efficient than solar water-splitting experiments of its kind.A new kind of solar panel has achieved 9% efficiency in converting water into hydrogen and oxygen–mimicking a crucial step in natural photosynthesis. Outdoors, it represents a major leap in the technology, nearly 10 times more efficient than solar water-splitting experiments of its kind.