Quantum cutting in Yb-doped lead halide perovskites has attracted considerable interest as a route to spectral conversion, with the potential to transform a single ultraviolet or visible photon into two near-infrared photons suitable for silicon photovoltaics.[1,2] Detailed balance calculations indicate that quantum cutting could significantly increase the theoretical efficiency limit of single-junction solar cells, but does not substantially improve the efficiency limit of tandem solar cells.[3] Even so, spectral shaping via quantum cutting provides several unique opportunities for tandems, broadening the range of optimal top-cell bandgaps from 1.7 eV to 1.45 eV depending on the quantum cutting bandgap. This opens the possibility of employing more stable neat-iodide perovskite absorbers while potentially improving ultraviolet utilization through improved external quantum efficiency.

To evaluate the practical feasibility of this approach, we combined experimental measurements with density functional theory calculations to investigate the reproducibility of quantum cutting in Yb-doped halide perovskites. Near-infrared down-conversion was consistently observed across multiple halide compositions and Yb concentrations, reproducing both the bandgap threshold for efficient down-conversion and optimal Yb concentration.[4] However, we did not observe photoluminescence quantum yields above 100%, suggesting that reproducible quantum cutting is not achieved under the conditions examined.

Density functional theory calculations were used to probe the local defect chemistry underlying this behavior. While isolated Yb-related defect complexes at low dopant concentrations can, in principle, support quantum cutting, these configurations are not strongly favored thermodynamically. Instead, Yb clustering becomes increasingly favorable, producing asymmetrical mid-gap electronic states that suppress quantum cutting.

These combined experimental and computational results indicate that although quantum cutting remains physically plausible in Yb-doped lead halide perovskites, its realization is highly sensitive to the local dopant environment and is therefore not intrinsically reproducible. Future progress will likely require strategies that control local defect configurations, including co-doping, defect engineering, or alternative synthetic approaches.