Photosensitizers absorb sunlight and pass that energy along to generate electricity or drive chemical reactions. Scientists watched what happened when light hit an inexpensive photosensitizer, iron carbene, and discovered it can respond in two competing ways, only one only one of which allows electrons to flow into the devices or reactions where they’re needed. It took this desired path about 60% of the time. The ultimate goal is to design cheap photosensitizers for specific tasks that are close to 100% efficient.