Three applications of ultrafast transient absorption spectroscopy of semiconductor thin films: spectroelectrochemistry, microscopy, and identification of thermal contributions

This review describes three recent developments in ultrafast transient absorption spectroscopy that have revealed new insights into the dynamics of photogenerated charge carriers in solution-processed semiconductor thin films. Transient absorption spectroelectrochemistry, in which transient absorption spectra are collected on a semiconductor film immersed in electrolyte solution under an applied potential, provides information about the dependence of transport of photogenerated charges on interfacial electronic structure. Ultrafast transient absorption microscopy enables measurement of excited state dynamics with sub-micron spatial resolution, which has been used to investigate the influence of film morphology on local excited state dynamics and image directly charge transport in solution-processed organic and hybrid organic–inorganic lead-halide perovskite semiconducting films. Finally, the recent identification of significant thermal contributions to the transient absorption spectra of organic and metal oxide semiconductor films is discussed, along with its potential implications for future measurements.