Scintillation as an Extreme Exciton Density Regime in Colloidal Nanocrystals

Colloidal semiconductor nanocrystals (NCs) have emerged as versatile light emitters for a broad range of applications, where they are typically operated in the dilute- or single-exciton regime. Scintillation under ionizing radiation, however, represents a fundamentally different mode of operation. A single absorbed X-ray photon can generate a large number of electron–hole pairs within a nanoscale interaction volume, driving individual NCs into extreme exciton occupancies. In this Perspective, we argue that scintillation in NCs should be viewed as an extreme exciton-density problem and show how simple occupancy considerations impose fundamental limits on achievable scintillation light yield. We further outline two complementary strategies to overcome these limitations: (i) engineering NCs for enhanced multiexciton radiative yields and (ii) designing NC composites that redistribute deposited energy across larger NC populations. We anticipate that exciton-density engineering will provide a unifying framework for designing the next generation of NC scintillators.