Snapshot measurement of the threshold excitation intensity of TTA-UC systems

Threshold excitation intensity is a key parameter for characterizing triplet-triplet annihilation photon upconversion (TTA-UC) systems, expected for diverse applications, including management of the sunlight spectrum. However, its measurement is a laborious and time-consuming process. In this article, we propose a simple and quick method for determining the threshold intensity from a snapshot of the emission image. The proposed method significantly shortens the measurement time compared to that for the conventional, widely used intensity-by-intensity method; it can be within a second. Its accuracy was confirmed to be comparable to that of the conventional method.