Improvement of S/N ratio in simultaneous photoacoustic and photoluminescence measurements by utilizing Helmholtz resonance

Accurate estimation of internal quantum efficiency (IQE) is essential for a comprehensive understanding of carrier dynamics in light-emitting materials in optical devices. We proposed simultaneous photoacoustic (PA) and photoluminescence measurements as a method for estimating accurate IQE values. This method detects the heat generated by non-radiative recombination as well as the light generated by radiative recombination, and this reduces the need to use theoretical models and assumptions for IQE estimation, unlike conventional methods that measure only radiative recombination processes. In some cases, however, there is a problem of heat generated outside of the measurement point being mixed into the PA signal. HF measurement reduces the mixing of false signals, but the PA signal intensity itself deceases with frequency, resulting in a poor S/N ratio. In this study, we have significantly improved the S/N ratio of PA measurements at HF by two measures in the microphone method we use for PA measurements: increasing the air pressure in the cell and utilizing Helmholtz resonance.