Ultrafast transient absorption measurements of photocarrier dynamics in PdSe.

We investigate the photocarrier dynamics in bulk PdSe, a layered transition metal dichalcogenide with a novel pentagonal structure and unique electronic and optical properties. Using femtosecond transient absorption microscopy, we study the behavior of photocarriers in mechanically exfoliated bulk PdSe flakes at room temperature. By employing a 400 nm ultrafast laser pulse, electron-hole pairs are generated, and their dynamics are probed using an 800 nm detection pulse. Our findings reveal that the lifetime of photocarriers in bulk PdSe is approximately 210 ps. Furthermore, by spatially resolving the differential reflection signal, we determine a photocarrier diffusion coefficient of about 7.3 cm s. Based on these results, we estimate a diffusion length of around 400 nm and a photocarrier mobility of approximately 300 cm V s. These results shed light on the ultrafast optoelectronic properties of PdSe, offer valuable insights into photocarriers in this emerging material, and enable design of high-performance optoelectronic devices based on PdSe.