Ultrafast Anisotropic Evolution of Photoconductivity in Sb 2 Se 3 Single Crystals.

The antimony chalcogenide crystals are composed of quasi-one-dimensional [Sb 4 X 6 ] n ribbons, which lead to strong anisotropic optical and electronic properties. An attempt to exploit photoconductivity anisotropy in the device fabrication may introduce a rewarding strategy to propel the development of the antimony chalcogenide solar cells. To achieve this, understanding of the dynamic evolution of the photoconductivity anisotropy is required. Here, the photoconductivities along different lattice directions in an antimony selenide single crystal are investigated by time-resolved terahertz spectroscopy. We find that electron trapping results in a variation of the photoconductivity anisotropy accompanied by a decrease in the photoconductivity magnitude, while electron-hole recombination only reduces the magnitude but does not affect the anisotropy. Therefore, measuring the temporal evolution of photoconductivity anisotropy can provide a wealth of information regarding the nature of the photocarrier and also render a probe to selectively evaluate the photoconductivity decay mechanisms.