Ultrafast Photocarrier Dynamics and Nonlinear Optical Absorption of a Layered Quaternary AgInP₂S₆ Crystal

Abstract

Layered quaternary metal thio/selenophosphates exhibit composition-dependent physical properties and have valuable applications in optoelectronic devices. Exploring their optical properties and photoexcited carrier dynamics is a prerequisite for their device design. Here, the ultrafast photocarrier dynamics and nonlinear absorption of a bulk AgInP2S6 crystal, a new member of this material family, are investigated by employing photoluminescence, time-resolved transient optical spectroscopies, and intensity-dependent transmission. The AgInP2S6 exhibits defect-assisted photoluminescence with more effective excitation under defect-state absorption and two-photon absorption at 800 nm. After initial intraband relaxation, the interband-excited carriers naturally accumulate at the conduction band minimum or valance band maximum, and then most of the nonequilibrium carriers relax via interband nonradiative recombination while the rest are transferred to the defect bands. Following that, the nonequilibrium carriers in the defect bands will first relax to the bottoms of the defect bands and finally recombine there. As compared with its analogue CuInP2S6, the substitution of Cu with Ag results in the variation of the two-photon absorption coefficient as well as the increase in carrier relaxation times due to the accompanying defect change. These findings provide microscopic insights into the optical response process of AgInP2S6 and valuable references for developing its optoelectronic devices.

Mode-locking pulse generation based on lead-free halide perovskite CsCu2I3 micro-rods with high stability

“…This might be associated with the susceptibility of materials to lattice defects, leading to optical transition, and band filling of intermediate or defective states. 60,61 Hence, the electronic band structures of CsCu 2 I 3 with Cs, Cu, and I atomic defects are simulated by DFT (as shown in Fig. S9 and S10, ESI †).…”

AgScP2S6 van der Waals Layered Crystal: A Material with a Unique Combination of Extreme Nonlinear Optical Properties

“…21 Later the same group reported a detailed study on NLO response and ultrafast dynamics of photogenerated carriers in the AgInP 2 S 6 crystal. 22 Recently our group demonstrated NLO properties of the Cu 0.33 In 1.34 P 2 S 6 crystal at 1032 nm excitation. 23 Building on these previous works, in this letter we report on the characterization of the third order NLO response from another material from same thio-phosphate family, silver scandium thiophosphate (AgScP 2 S 6 ).…”

“…Tian et al investigated TPA response from the CuInP 2 S 6 (CIPS) crystal at 800 nm . Later the same group reported a detailed study on NLO response and ultrafast dynamics of photogenerated carriers in the AgInP 2 S 6 crystal . Recently our group demonstrated NLO properties of the Cu 0.33 In 1.34 P 2 S 6 crystal at 1032 nm excitation …”

“…Clearly, AgScP 2 S 6 evinces an absorption edge at 2.80 eV; however, PL emission peaks at 2.0 eV, resulting in an abnormal stoke shift of 0.8 eV. We presume that the broad PL emission most likely arises from radiative recombination of generated hot carriers from the localized defect states with initial intraband relaxation to conduction band (CB) minimum . Probing the exact origin of such emission may require further work using time-resolved spectroscopic measurements.…”

“…We presume that the broad PL emission most likely arises from radiative recombination of generated hot carriers from the localized defect states with initial intraband relaxation to conduction band (CB) minimum. 22 Probing the exact origin of such emission may require further work using time-resolved spectroscopic measurements. We note that small peaks in the PL spectra are due to the stitching effects of the data collection software, occurring every 100 nm for high-resolution spectrometry.…”