Quantum-Cutting Ytterbium-Doped CsPb(Cl1–xBrx)3 Perovskite Thin Films with Photoluminescence Quantum Yields over 190%

Abstract

A two-step solution-deposition method for preparing ytterbium-doped (Yb 3+ ) CsPb(Cl 1– x Br x ) 3 perovskite thin films is described. Yb 3+ -doped CsPb(Cl 1– x Br x ) 3 films are made that exhibit intense near-infrared photoluminescence with extremely high quantum yields reaching over 190%, stemming from efficient quantum cutting that generates two emitted near-infrared photons for each absorbed visible photon. The near-infrared Yb 3+ f – f photoluminescence is largely independent of the anion content ( x ) in CsPb(Cl 1– x Br x ) 3 films with energy gaps above the quantum-cutting threshold of twice the Yb 3+ f – f transition energy, but it decreases abruptly when the perovskite energy gap becomes too small to generate two Yb 3+ excitations. Excitation power dependence measurements show facile saturation of the Yb 3+ luminescence intensity, identifying a major challenge for future solar applications of these materials.