Quantum-cutting Luminescence in CsPbCl3:Yb3+ Perovskite Nanocrystals
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CsPbCl3 perovskite nanocrystals doped with ytterbium have recently been discovered as highly efficient blue-to-NIR quantum-cutting phosphors. However, the quantum-cutting efficiency has been measured to decrease with increasing intensity of incident light. While CsPbCl3:Yb3+ could increase the efficiency of photovoltaic devices, this saturation effect prevents effective application. Different mechanism for quantum-cutting and luminescence saturation have been proposed. As a result of this ambiguity, it is difficult to find a solution to prevent saturation. In this thesis, we further investigate a proposed mechanism behind quantum-cutting and luminescence saturation in Yb3+-doped perovskites. We measured a temperature dependence of the NIR-emission intensity in CsPbCl3:Yb3+ nanocrystals that is qualitatively in line with a mechanism without a proposed intermediate trap state in the quantum cutting mechanism. This is in contrast to the measured temperature dependent saturation, which qualitative is in line with a mechanism with an intermediate trap state. Time dependent measurements showed no overshoot in the luminescence intensity during the first few milliseconds after inset of excitation, which should be visible if quantum cutting occurs through the proposed quantum cutting mechanism that involves dopant pairs.