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 $\mathrm{\Delta }$OD. 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.

中文翻译：

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超高灵敏瞬态吸收光谱仪

瞬态吸收 (TA) 光谱被认为是反映光电和光催化材料中光生载流子超快动力学的强大技术。然而，受其灵敏度的限制，在太阳能材料的TA测量中，光生载流子密度通常远高于实际工作条件下的光生载流子密度。在这里，我们提出了用于超高灵敏度 TA 光谱仪的 kHz 宏脉冲和 MHz 微脉冲技术的组合，该技术提高了对 10 ^-7水平的灵敏度$\mathrm{\Delta }$外径。它使我们能够研究由极低功率泵浦的超快载流子动力学，这可以避免多体相互作用的影响和与高载流子密度相关的非线性效应。这项工作提供了一种具有超高灵敏度的新颖的TA方法，它将在研究工作条件下半导体的载流子动力学方面发挥重要作用。