Photon Statistics from Yb3+-Doped CsPbCl3 Are Inconsistent with Quantum Cutting

CsPb(Cl1–xBrx)3:Yb3+ has been widely reported as a broadband quantum-cutting material with a photoluminescence quantum yield exceeding 100%, making it a promising candidate for enhancing the blue–green spectral response of silicon photovoltaics. Many groups have reproduced absolute photoluminescence quantum yields over 100%, but others have struggled to obtain such high values. Here, we test the quantum-cutting capabilities of CsPbCl3:Yb3+ nanocrystals and bulk material using photon-correlation analysis. A quantum-cutting material is expected to exhibit photon bunching, but our experiments on CsPbCl3:Yb3+ show no such behavior. In fact, we observe the opposite─antibunching─under focused-excitation conditions. This observation can be explained with the previously established Auger-quenching pathway in CsPbCl3:Yb3+. Our results thus confirm high-power Auger quenching but question earlier descriptions of quantum cutting in CsPb(Cl1–xBrx)3:Yb3+.