Abstract
Photoluminescence (PL) quantum yield (QY), which is defined as the ratio of emitted to absorbed photons, is the central quantity that characterizes light-emitting materials. It is an important parameter to assess the light efficiency of new materials, as well as identify novel photophysical mechanisms.
While QY measurements are performed as standard in research and industry, accurate measurements are challenging. Here, we show that, besides known inaccuracies, PL QY measurements exhibit a surprising systematic bias.
QY values are underestimated by a factor of two or more for samples with lower absorption, which can even lead to misinterpretation of results. We combine PL QY measurements of diluted Rhodamine 6G and two different semiconductor quantum dot solutions, via the standard integrating sphere method, with analytical modeling and ray-tracing simulations and find that, independent of the setup and luminescence mechanism, all measurements suffer from the same systematic underestimation of the QY.
Through statistical analysis of the measured emitted and absorbed photon numbers, we uncover the origin of this underestimation in the asymmetry of the ratio distribution for low absorption, together with setup-specific features, such as signal offsets and nonlinearities. We suggest a robust calibration procedure to correct for this bias for precise evaluation of the QY in materials used for bioimaging, biosensing, and optoelectronic or photovoltaic devices.