‘Quantum cutting’ is a process by which absorption of a single high-energy photon, corresponding to incident light in the UV spectral region, results in the emission of two photons of lower energy, in the visible region. The process is highly efficient and has important applications for improving the spectral range of solar photovoltaic cells, as well as providing more efficient domestic lighting. With reference to articles by Huang et al. (Chem. Soc. Rev. 2013, 42, 173) and Lorbeer et al. (Chem. Commun., 2010, 46, 571), explain why Gd, in conjunction with other lanthanoids, is important for developing this technology.