Singlet fission breaks 'ceiling' of solar cells for 130% quantum yield

Researchers from Kyushu University and Johannes Gutenberg University Mainz have surpassed the traditional “physical ceiling” of solar energy conversion by achieving a quantum yield of 130% using a novel “spin-flip” emitter. This breakthrough challenges the long-standing Shockley–Queisser limit, which restricts conventional solar cells to a one-photon-to-one-electron conversion, with excess photon energy lost as heat. Their approach leverages singlet fission (SF), a process where one high-energy singlet exciton splits into two lower-energy triplet excitons, theoretically allowing one photon to generate two energy carriers. The key innovation lies in a molybdenum-based metal complex that acts as a “spin-flip” emitter, selectively capturing triplet excitons while suppressing energy loss via Förster resonance energy transfer (FRET). By flipping the electron spin during light absorption, this complex aligns spins to efficiently harvest the multiplied excitons produced by singlet fission. Paired with tetracene-based materials