No abstract

Quantum cutting (QC) is a process that can split one high-energy photon into two or more low-energy photons.1-4 As an attractive mechanism, it has been extensively explored for acquiring high quantum efficiency (QE) of more than 100%.5-8 Here, we report the first experimental observation of multiphoton QC with ultrahigh QEs in CaF2:Yb polycrystalline. Under 266 nm excitation, an internal quantum efficiency as high as ~285% was achieved, indicating that one ultraviolet (UV) photon was split into more than two ~1000 nm near infrared (NIR) photons. Photovoltaic experiments demonstrated that the polycrystalline increased the output power of a polycrystalline silicon solar cell by more than 200% in the case of 266 nm irradiation. Spectral analysis confirmed that the ultrahigh QE originated from efficient cooperative absorptions of Yb-tetramers and Yb-trimers and individual emission of single Yb3+ ions. This study provides a promising approach for improving spectral response of silicon solar cells and detectors in the UV region.