Refining Photothermal Deflection Spectroscopy: Incorporating Reflectance for Enhanced Accuracy in Light‐Absorption Measurements

A method for measuring light absorption using photothermal deflection spectroscopy (PDS) is investigated. Typical reflectance and transmittance (R & T) absorption measurements have low spectral resolution (SR) with standard setups. It is believed that absorption measurements using PDS solve this problem because of its high sensitivity, even at a high SR. However, accurate absorption measurements have not been obtained using conventional PDS. The reflectance of the sample must be considered in the absorptance calculations. Various absorption measurement methods are compared and a novel calculation method for accurate PDS absorption measurements is proposed. A sample with quantum structures is fabricated and PDS measurements are performed. Exciton absorption peaks are also observed. The high SR of PDS is demonstrated and the measured exciton absorption peaks are confirmed using piezoelectric photothermal measurements. Furthermore, it is confirmed that the absolute values of absorptance derived from the R & T and PDS measurements agree well. The new PDS absorption measurement technique enables to obtain accurate absorption characteristics, which are indispensable for designing and optimizing optoelectronic devices. This study presents a method for conducting accurate absorption measurements using photothermal deflection spectroscopy (PDS). The surface reflectance must be considered when calculating the absorptance. It is demonstrated how to estimate the reflectance of a sample in a liquid. The light absorptance of a quantum structure with high accuracy is measured by using PDS.