Temperature-Dependent Ultrafast Charge Carrier Dynamics in Amorphous and Crystalline Sb₂Se₃ Thin Films

Abstract

The Earth abundant polycrystalline antimony selenide (Sb2Se3) thin film is considered to be a potential photovoltaic material for their appropriate band gap, higher absorption coefficient, and nontoxicity. Interband gap defect states play a major role for efficient solar devices, which depends on the crystallinity of the materials. In the present investigation, we have synthesized an amorphous Sb2Se3 thin film by following the thermal evaporation technique and have also converted the film to crystalline after vacuum annealing it at 250 °C. Both amorphous and crystalline thin films were characterized by several analytical techniques, XRD, FE-SEM, optical absorption, XPS, and UPS spectroscopy. The interband gap defect density was found to be much higher in the amorphous thin film as compared to that of the crystalline one. To understand the charge carrier dynamics of the photoexcited Sb2Se3 thin film, femtosecond broad-band pump–probe spectroscopy has been employed at cryogenic temperature (5 K) and room temperature (300 K). Carrier trapping and recombination dynamics for both the films were found to be faster at 5 K than at 300 K and were attributed to higher carrier mobility at high temperatures. Understanding carrier dynamics of this photovoltaic materials are immensely useful for designing efficient devices.

Ultrafast Hot Electron Transfer and Trap-State Mediated Charge Carrier Separation toward Enhanced Photocatalytic Activity in g-C3N4/ZnIn2S4 Heterostructure

“…This again confirms the designation of trap states (850 nm for LT and 1200 nm for ST). 38 In the TA spectra of CN/ZIS (Figure 5b), a significant decrease in ESA signal intensity is observed as compared to CN. As we compare the signal intensity for both the region, the ESA II signal is diminished drastically in few tens of ps, while the ESA I signal decays significantly slower in few hundreds of picoseconds.…”

“…Both the signals are fitted with three distinct decay time scales (HSE 0.7 ps, 17.7 ps, and >1 ns; BSE 1.2 ps, 27.7 ps, and >1 ns). The first two time components are assigned to the trapping of charge carriers in short-distance (ST) and long-distance (LT) trap states, respectively 11,38 The final component is associated with the trapping of charge carriers in the deep trap states and eventual recombination. 39,40 These charge trapping processes are schematically discussed in the Supporting Information (Figure S6) Now we have carried out ultrafast TA studies of the CN/ZIS heterostructure after 320 nm pump excitation, and TA spectra are shown in Figure 4a.…”

Effect of Surface Ligand on Chemical Interface Damping in Nonstoichiometric Cu2–xS Semiconductor Nanocrystals: A Direct Correlation between Ultrafast Carrier Dynamics and Photoconductivity

“…Transient ultrafast spectroscopic measurements were performed using a setup described in our earlier studies . Briefly, a 80 MHz Ti:sapphire modelock laser, providing pulses at 800 nm, with a typical energy of 500 mW and a 35 fs duration.…”

“…The sample was placed in a 2 mm thick cuvette to acquire transient absorption. The acquired data has been analyzed by Surface Xplorer software. , …”

“…Transient ultrafast spectroscopic measurements were performed using a setup described in our earlier studies. 22 Briefly, a 80 MHz Ti:sapphire modelock laser, providing pulses at 800 nm, with a typical energy of 500 mW and a 35 fs duration. The regenerative amplifier (Coherent, Astrella) has been employed to generate sub-45 fs amplified 1 kHz laser pulses with a maximum power of 5 mJ.…”