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Layered Hybrid Perovskites for Highly Efficient Three-Photon Absorbers: Theory and Experimental Observation
摘要： Multiphoton absorption may find many technological applications, such as enhancing the conversion efficiency of solar cells by the utilization of sub-band-energy photons, below-bandgap photodetection through the simultaneous absorption of several infrared photons for photocurrent generation, or light frequency upconversion for high-resolution, 3D imaging. To enhance multiphoton absorption in semiconducting materials, one of the strategies is to explore low-dimensional excitons. Here, a quantum perturbation theory on a giant enhancement in three-photon absorption (3PA) arising from 2D excitons in multilayered crystals of organic–inorganic hybrid perovskites is presented. The maximal 3PA coefficient is predicted to be in the range of 2–7 cm3 GW?2 at 1100 nm, the largest values reported so far for any 2D and bulk semiconductors at room temperature. Excellent agreement between theory and the experimental findings unambiguously demonstrates a pivotal role in the enhancement of 3PA played by 2D excitons. The theory predicts that the resonant 3PA coefficient should be enhanced further by at least two orders of magnitude with very low temperature. The findings are essential for understanding giant 3PA arising from 2D excitons in layered hybrid perovskites and may open new pathways for highly efficient conversion from infrared light energy to either electrical energy or higher-frequency light emission/lasing.
关键词： nonlinear optics,three-photon absorbers,2D excitons,hybrid perovskites
更新于2025-09-04 15:30:14
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Efficient synthesis of BiFeO3 by the microwave-assisted sol-gel method: “A” site influence on the photoelectrochemical activity of perovskites
摘要： BiFeO3 (BF) and LaFeO3 (LF) perovskites were synthesized using a microwave-assisted (MW) and sol-gel (SG) methods. XRD, XPS, TEM, UV-DRS techniques were applied to study physicochemical properties of perovskites. In addition, Incident Photon-to-Current Efficiency (IPCE) measurements, Linear Sweep Voltammetry (LSV) and impedance spectroscopy were used to characterize electrochemical properties of the material. The band gap energy increases in the following way: BF-MW (2.05 eV), LF-MW (2.18 eV), BF-SG (2.26 eV) and LF-SG (2.54 eV), demonstrating a remarkable influence of the synthesis method on the optical and electronic properties of the materials. Furthermore, XRD showed a significant impact of the synthesis methods on the crystal structure. Perovskites synthesized under WM irradiation showed a pure crystal structure compared to the perovskites prepared by SG method, which contained some admixtures. IPCE shows that LF-MW has a better charge separation ability compared to BF-MW. However, BF-SG showed the highest activity. Temperature programmed reduction tests (TPR) revealed a better ability of BiFeO3 to adsorb/desorb oxygen, compared to LaFeO3. XPS measurements pointed at the presence of Fe4+. Finally, the photocatalytic activity of the perovskites was tested in solar water-splitting as a function of the synthesis method and presence of Bi and La in “A” sites of the ABO3 perovskites. We postulate, that the Jahn-Teller distortion effect in LF-MW increases its catalytic activity by decreasing the binding energy compared to BF-MW.
关键词： Microwave-assisted synthesis,Jahn-Teller distortion,Photocatalysts,Photoelectrochemical water splitting,Perovskites
更新于2025-09-04 15:30:14