Investigation into the carrier recombination in Sb2Se3: Photo thermal effect, trapped carrier absorption and hot carrier cooling

Abstract

Understanding the carrier recombination processes in Sb₂Se₃ is essential for its optoelectronic applications. In this work, carrier recombination dynamics in Sb₂Se₃ were studied by broad band transient absorption spectroscopy. Firstly, the contribution of photothermal effect to the transient absorption spectrum was thoroughly discussed. It is confirmed that the excited state absorption (ESA) band with lifetime of several nanoseconds results from co-contribution of photo thermal effect and deep trapped carrier absorption. Secondly, the features of transient absorption spectrum on picosecond time scale were interpreted. The short-lived ESA band around 1000 nm was assigned to shallow trapped carrier absorption, while not band gap renormalization (BGR) or free carrier absorption. By globally fitting the transient absorption spectrum, the hot carrier cooling time and time constant for free carrier relax into deep trap state were determined to be 0.25∼0.45 ps and 3.1∼8.7 ps, respectively. Finally, we built up the carrier recombination model of Sb₂Se₃. The experimental results in this work will improve the understanding on the carrier recombination in Sb₂Se₃.