Ultrafast transient absorption measurements of photocarrier dynamics in PdSe ₂

We investigate the photocarrier dynamics in bulk PdSe₂, 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 PdSe₂ 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 PdSe₂ is approximately 210 ps. Furthermore, by spatially resolving the differential reflection signal, we determine a photocarrier diffusion coefficient of about 7.3 cm² s^-1. Based on these results, we estimate a diffusion length of around 400 nm and a photocarrier mobility of approximately 300 cm² V^-1 s^-1. These results shed light on the ultrafast optoelectronic properties of PdSe₂, offer valuable insights into photocarriers in this emerging material, and enable design of high-performance optoelectronic devices based on PdSe₂.