Solar Cells Beat the 100% Rule with a New Energy Trick

A team of researchers from Japan and Germany discovered a way to make solar cells produce more useful energy than the light they absorb, reaching about 130 % efficiency. The trick involves a special molybdenum metal complex that can capture extra energy created by a process called singlet fission. In normal solar cells, only about one‑third of sunlight can be used because low‑energy photons are too weak and high‑energy ones lose heat. This limitation is known as the Shockley‑Queisser limit. Singlet fission can turn one photon into two lower‑energy excitations, potentially doubling the usable energy. The challenge has been to keep these extra excitations from being lost through a mechanism called Förster resonance energy transfer (FRET). The Japanese‑German team solved this by designing a metal complex that “flips” the spin of an electron when it absorbs or emits near‑infrared light, allowing it to snag the triplet excitons produced by fission.By fine‑tuning the energy levels of the complex, they minimized FRET losses and achieved quantum yields of about 1. 3 excitations per absorbed photon. This means that for every photon the system takes in, it can generate more than one energy carrier—an outcome impossible with conventional solar cells. The work was a joint effort between Kyushu University and Johannes Gutenberg University Mainz. A visiting graduate student from the German group introduced a material that had been studied there for years, sparking the collaboration. Together they tested the system in solution with tetracene, a known fission material, and saw the breakthrough efficiency. While still at the proof‑of‑concept stage, this strategy could be integrated into solid‑state devices. If successful, it would push solar technology beyond the current efficiency ceiling and could also benefit other fields like LEDs or quantum information devices, where efficient energy transfer is crucial. Future research will focus on making the materials stable in solid films and compatible with existing solar cell architectures. If these hurdles are cleared, we could see a new class of high‑efficiency solar panels that use every photon more fully than ever before.