Ultrahigh sensitive transient absorption spectrometer

Transient absorption (TA) spectroscopy is considered as a powerful technique that reflects the ultrafast dynamics of photogenerated carriers in photoelectric and photocatalysis materials. However, limited by its sensitivity, the photogenerated carrier density in TA measurements of solar energy materials is usually much higher than that in the real working condition. Here, we present a combination of kHz macro-pulse and MHz micro-pulse technique for an ultrahigh sensitive TA spectrometer, which improves the sensitivity to the 10^-7 level of ΔOD. It enables us to study ultrafast carrier dynamics pumped by very low power, which can avoid the influence of many-body interactions and the nonlinear effect associated with high carrier density. This work provides a novel TA method with ultrahigh sensitivity, which will play an important role in investigating the carrier dynamics of semiconductors in the working condition.