High-responsivity hybrid α-Ag2S/Si photodetector prepared by pulsed laser ablation in liquid

Novel nickel-immobilized-SiO2-TiO2 fine particles in the presence of cetyltrimethylammonium bromide as a catalyst for ultrasound-assisted-Kumada cross-coupling reaction

Kumada cross-coupling reaction is useful for producing biphenyls, where nickel and copper have been widely investigated as catalysts but mainly homogeneous ones. In this study, we investigated ultrasound-assisted-Kumada cross-coupling reaction over the heterogeneous catalysts in which Ni2+, Cu2+, or both was immobilized on aminopropylsilane-functionalized-SiO2-TiO2 prepared in the presence of cetyltrimethylammonium bromide (CTAB). The presence of CTAB effectively prevented the particle growth and therefore SiO2-TiO2 fine particles with high surface area (502 m2 g-1) were formed. The Ni2+-immobilized catalyst showed high catalytic activity for the ultrasound-assisted-Kumada cross-coupling reaction of a wide variety of substrates and was reusable three times. Performing the reaction under ultrasound irradiation was very effective in significantly accelerating the reaction rate compared with the conventional mechanical method. In contrast to Ni2+, Cu2+ was deposited on the support as crystalline Cu(OH)2 and the resulting catalysts with Cu2+ and Ni2+-Cu2+ were less active and less stable under the reaction conditions.

Design of Pentanary Mixed-Chalcogenides Ag2In2SiS6-xSex (x = 1, 2) Based on the Bucket Effect: Local Structural Difference and High-Performance Nonlinear-Optical Properties Realized by Partial Congener Substitution

Noncentrosymmetric chalcogenides are promising candidates for infrared nonlinear-optical (NLO) crystals, and exploring high-performance ones is a hot topic and challengeable. Herein, the combination of AgQ4, InQ4, and SiQ4 (Q = S, Se) units with different S/Se ratios resulted in the discovery of the tetrahedral chalcogenides Ag2In2SiS4Se2 (1) and Ag2In2SiS5Se (2). They both crystallize in the monoclinic Cc space group with different local structures. Co-occupied S/Se sites only exist in 2, and the arrangement of [In2SiQ3] six-membered rings builds different helical chains and 3D [(In2SiQ6)2-]n polyanionic frameworks in 1 and 2. They show balanced NLO performances, including phase-matchable moderate NLO responses (0.7 and 0.5 × AGS) and enhanced laser-induced damage thresholds (4.5 and 5.1 × AGS). Theoretical calculations reveal that their NLO responses are predominantly contributed by the AgQ4 and InQ4 units.

Role of substrate temperature on the performance of BaTiO3/Si photodetector prepared by pulsed laser deposition

In this study, the pulsed laser deposition (PLD) method was employed to fabricate nanostructured BaTiO3 films on glass and silicon substrates at varying temperatures. The structural analysis confirmed the formation of crystalline nanostructured BaTiO3 with mixed tetragonal and hexagonal phases, and the film deposited at 150 °C has the best crystallinity and largest particle size. The optical energy gap of the BaTiO3 nanostructure decreases from 3.94 to 3.84 eV, with increasing substrate temperature from 60 to 150 °C. Photoluminescence spectra of BaTiO3 films deposited at 25, 60, 100, and 150 °C exhibit emission peaks centered at 450, 512, 474, and 531 nm, respectively. Raman spectra of BaTiO3 films show E (LO), A (TO), E (LO) + TO, and B1 vibration modes. Hall measurements reveal that the mobility of the BaTiO3 film increases with temperature up to 100 °C and then decreases at 150 °C. The current-voltage characteristics of the BaTiO3/p-Si heterojunction, deposited over a temperature range of 25 to 150 °C, were investigated in the dark and under illumination. The heterojunctions exhibit rectifying properties, with the best rectification factor observed for the heterojunction prepared at 100 °C. The values of the ideality factor for the heterojunctions fabricated at 25, 60, 100, and 150 °C were 4.3, 3.8, 2.8, and 5, respectively. The study reveals an improvement in both the figures of merit and the photodetector performance with increased substrate temperature. The responsivity increases from 2.2 to 9.25 A/W as the deposition temperature rises from 25 to 100 °C. The detectivity (D*) and external quantum efficiency (EQE) of the photodetector prepared at the optimum substrate temperature of 100 °C, were found to be 4.62 × 1012 Jones and 114%, respectively, at 500 nm.

Effect of laser fluence on the optoelectronic properties of nanostructured GaN/porous silicon prepared by pulsed laser deposition

In this study, the fabrication of nanostructured GaN/porous Si by pulsed laser deposition (PLD) was demonstrated. The porous silicon was prepared using laser-assisted electrochemical etching (LAECE). The structural, optical, and electrical properties of GaN films were investigated as a function of laser fluence. XRD studies revealed that the GaN films deposited on porous silicon were nanocrystalline, exhibiting a hexagonal wurtzite structure along the (100) plane. Spectroscopic property results revealed that the photoluminescence PL emission peaks of the gallium nitride over porous silicon (GaN/PSi) sample prepared at 795 mJ/mm2 were centered at 260 nm and 624 nm. According to topographical and morphological analyses, the deposited film consisted of spherical grains with an average diameter of 178.8 nm and a surface roughness of 50.61 nm. The surface of the prepared films exhibited a cauliflower-like morphology. The main figures of merit of the nanostructured GaN/P-Si photodetectors were studied in the spectral range of 350-850 nm. The responsivity, detectivity, and external quantum efficiency of the photodetector at 575 nm under - 3 V were 19.86 A/W, 8.9 × 1012 Jones, and 50.89%, respectively. Furthermore, the photodetector prepared at a laser fluence of 795 mJ/mm2 demonstrates a switching characteristic, where the rise time and fall time are measured to be 363 and 711 μs, respectively.

High responsivity of VIS-NIR photodetector based on Ag2S/P3HT heterojunction

Ag₂S quantum dot (QD) photodetectors (PDs) have attracted a lot of attention in the field of imaging system and optical communication. However, the current Ag₂S PDs mainly works in the near-infrared band, and its detection ability in the visible band remains to be strengthened. In this paper, we used poly(3-hexylthiophene) (P3HT) with high carrier mobility and Ag₂S QDs to construct heterojunction PD. Stronger absorption in blends with polymer P3HT compared to single Ag₂S QDs. The optical absorption spectra show that the Ag₂S/P3HT has strong light absorption peak at 394 and 598 nm. The results show that P3HT significantly enhances the absorption of Ag₂S QDs from the visible to near-infrared band. The output characteristics, transfer characteristics and fast switching capability of the device at 405 nm, 532 nm and 808 nm were tested. The device has the responsivity of 6.05 A W^-1, 83.72 A W^-1and 37.31 A W^-1under 405 nm, 532 nm and 808 nm laser irradiation. This work plays an important role in improving the detection performance of Ag₂S QDs and broadening its applications in photoelectric devices for weak light and wide spectrum detection.