Tuning Ultrafast Carrier Dynamics and Broadband Photo-Response of High-Performance Sb₂Se₃ Thin Film Photodetectors: A Substrate Dependent Study

In the field of photodetectors, antimony selenide (Sb2Se3) is one of the materials exhibiting wideband photo response, characterized by its suitable bandgap and fast response time. However, apart from these fascinating properties, substrate compatibility plays a vital role in defining the device's efficiency. The present study investigates the varying broadband photo response of thermally grown antimony selenide (Sb2Se3) films on various substrates (Al2O3, SiO2, quartz, and pyramidal sapphire). The devices Au/Sb2Se3/Al2O3, Au/Sb2Se3/quartz, and Au/Sb2Se3/SiO(2 )show the highest responsivity of 79 mA/W in NIR, 150 mA/W in visible, and 245 mA/W in UV, respectively. Moreover, the device Au/Sb2Se3/Al2O3 demonstrated the fastest response time of 230 ms. Notably, the Sb2Se3 device on pyramidal-patterned sapphire shows the least responsivity across the wide band compared with other devices. To delve deeper into this variation in responsivity and significantly low photo response of the patterned sapphire film, we conducted a comprehensive investigation into the substrate's impact in generating photocarriers using ultrafast pump-probe spectroscopy along with XRD, RAMAN, and EDS data analysis. Further, an extensive study exploring pump power and pump wavelength dependencies sheds light on defect-mediated and polaron-mediated relaxation mechanisms. Additionally, distinct transient reflectance peaks and variable carrier relaxation lifetimes underscore the dynamic influence of substrate selection on high-performance photodetectors for practical applications.