Photon Statistics as a Tool to (Dis)Prove Cooperative Energy Transfer Quantum Cutting in Near-Infrared Emitting Materials

High Resolution Image Download MS PowerPoint Slide Spectral conversion of sunlight can enhance solar cell efficiencies by shifting short-wavelength photons to longer wavelengths, where the photovoltaic response is stronger. This can be realized with near 100% energy efficiency by materials capable of quantum cutting . These emit two longer-wavelength photons, following the absorption of one shorter-wavelength photon. Although various quantum-cutting materials have been reported, follow-up research has often disproved initial claims. Here, we demonstrate that photon correlation analysis is a universal strategy to unambiguously identify quantum cutting. We investigate two materials, YPO 4 codoped with Tb 3+ and Yb 3+ and yttrium aluminum garnet (YAG) codoped with Ce 3+ and Yb 3+ . Both are reported to perform quantum cutting via blue light absorption followed by cooperative energy transfer to near-infrared-emitting Yb 3+, but some studies have cast doubts for YAG:Ce 3+,Yb 3+ . Our correlation analysis demonstrates bunched emission for YPO 4:Tb 3+,Yb 3+, confirming quantum cutting. In contrast, YAG:Ce 3+,Yb 3+ shows Poissonian emission statistics, disproving its quantum-cutting capability, despite previous claims.