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1.
    
Tin halide perovskites are potential alternatives of lead halide perovskites. However, the easy oxidation of Sn2+ to Sn4+ brings in a challenge. Recently, layered two-dimensional hybrid tin halide perovskites have been shown to partially resist the oxidation process because of the presence of hydrophobic organic molecules. Consequently, such layered hybrid perovskites are being explored for optoelectronic applications. The optical properties of layered tin halide perovskites depend on the interlayer separation and the dielectric mismatch between the organic and inorganic layers. Intercalation (insertion) of a molecular species between the layers modifies the interlayer interactions affecting the optical properties of layered hybrid perovskites. We investigated the effect of hexafluorobenzene (HFB) intercalation in phenethylammonium tin iodide [(PEA)2SnI4] using temperature-dependent (6 K to 300 K) photoluminescence (PL). HFB intercalation increases the bandgap. A strong PL quenching is observed in pristine (PEA)2SnI4 below 150 K, probably because of the presence of non-emissive states. HFB intercalation suppresses the influence of such non-emissive states resulting in an increase in PL intensity at the cryogenic temperatures. Our results highlight that a simple molecular intercalation (non-covalent interaction) into layered hybrid perovskites can significantly tailor the electronic and optical properties.  相似文献   

2.
    
Here, we investigate in detail the impact of the size of the methylammonium iodide (MAI) reactants in the mechanochemical powder synthesis of the halide perovskite methylammonium lead iodide (MAPbI3). Morphology and structural characterizations by scanning electron microscopy and X-ray diffraction reveal that with increasing MAI reactant size, the particle size of the perovskite powder increases, while its defect density decreases, as suggested by nuclear quadrupole resonance spectroscopy and photoluminescence investigations. The reason for this behavior seems to be associated to the sensitive influence of the MAI size on the time durations of MAPbI3 synthesis and delayed MAPbI3 crushing stage during ball milling. Thus, our results emphasize the high importance the reactant properties have on the mechanochemical synthesis of halide perovskites and will contribute to enhance the reproducibility and control of the fabrication of halide perovskites in powder form.  相似文献   

3.
    
In layered hybrid perovskites, such as (BA)2PbI4 (BA=C4H9NH3), electrons and holes are considered to be confined in atomically thin two dimensional (2D) Pb–I inorganic layers. These inorganic layers are electronically isolated from each other in the third dimension by the insulating organic layers. Herein we report our experimental findings that suggest the presence of electronic interaction between the inorganic layers in some parts of the single crystals. The extent of this interaction is reversibly tuned by intercalation of organic and inorganic molecules in the layered perovskite single crystals. Consequently, optical absorption and emission properties switch reversibly with intercalation. Furthermore, increasing the distance between inorganic layers by increasing the length of the organic spacer cations systematically decreases these electronic interactions. This finding that the parts of the layered hybrid perovskites are not strictly electronically 2D is critical for understanding the electronic, optical, and optoelectronic properties of these technologically important materials.  相似文献   

4.
Babu KS  Kumar TR  Haridoss P  Vijayan C 《Talanta》2005,66(1):160-165
Nanoclusters of CdS and PbS were prepared using two different organic solvents as stabilizers in order to understand the factors affecting their formation and stabilization. Growth of the nanoclusters was monitored by optical absorption spectroscopy at regular intervals of time. Mean cluster size was characterized by X-ray diffraction (XRD). The surface structure of nanoclusters was analyzed using infrared (IR) spectroscopy. Spectroscopic studies under identical experimental conditions reveal interesting correlations between the stability of the nanoclusters formed, the nature of the solvent and the size of metal ion involved, leading to a better understanding of nanocluster formation.  相似文献   

5.
    
Despite the progressive enhancement in the flexibility of Pb-based perovskites for optoelectronic applications, regrettably, they are facing two main challenges; (1) instability, which originates from using organic components in the perovskite structure, and (2) toxicity due to Pb. Therefore, new, stable non-toxic perovskite materials are demanded to overcome these drawbacks. The research community has been working on a wide variety of Pb-free perovskites with different molecular formulas and dimensionality. A variety of Pb-free halide double perovskites have been widely explored by different research groups in search for stable, non-toxic double perovskite material. Especially, Cs-based Pb-free halide double perovskite has been in focus recently. Herein, we present a review of theoretical and experimental research on Cs-based Pb-free double halide perovskites of structural formulas Cs2M+M3+X6 (M+ = Ag+, Na+, In+ etc.; M3+= Bi3+, In3+, Sb3+; X = Cl−, Br−, I¯) and Cs2M4+X6 (M4+ = Ti4+, Sn4+, Au4+ etc.). We also present the challenges faced by these perovskite compounds and their current applications especially in photovoltaics alongside the effect of metal dopants on their performance.  相似文献   

6.
    
A remarkable PL enhancement by 12 fold is achieved using pressure to modulate the structure of a recently developed 2D perovskite (HA)2(GA)Pb2I7 (HA=n-hexylammonium, GA=guanidinium). This structure features a previously unattainable, extremely large cage. In situ structural, spectroscopic, and theoretical analyses reveal that lattice compression under a mild pressure within 1.6 GPa considerably suppresses the carrier trapping, leading to significantly enhanced emission. Further pressurization induces a non-luminescent amorphous yellow phase, which is retained and exhibits a continuously increasing band gap during decompression. When the pressure is released to 1.5 GPa, emission can be triggered by above-band gap laser irradiation, accompanied by a color change from yellow to orange. The obtained orange phase could be retained at ambient conditions and exhibits two-fold higher PL emission compared with the pristine (HA)2(GA)Pb2I7.  相似文献   

7.
    
A remarkable PL enhancement by 12 fold is achieved using pressure to modulate the structure of a recently developed 2D perovskite (HA)2(GA)Pb2I7 (HA=n‐hexylammonium, GA=guanidinium). This structure features a previously unattainable, extremely large cage. In situ structural, spectroscopic, and theoretical analyses reveal that lattice compression under a mild pressure within 1.6 GPa considerably suppresses the carrier trapping, leading to significantly enhanced emission. Further pressurization induces a non‐luminescent amorphous yellow phase, which is retained and exhibits a continuously increasing band gap during decompression. When the pressure is released to 1.5 GPa, emission can be triggered by above‐band gap laser irradiation, accompanied by a color change from yellow to orange. The obtained orange phase could be retained at ambient conditions and exhibits two‐fold higher PL emission compared with the pristine (HA)2(GA)Pb2I7.  相似文献   

8.
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Two thin-film 2D organic-inorganic hybrid perovskites, i.e., 2-phenylethylammonium lead iodide (PEPI) and 4-phenyl-1-butylammonium lead iodide (PBPI) were synthesized and investigated by steady-state absorption, temperature-dependent photoluminescence, and temperature-dependent ultrafast transient absorption spectroscopy. PBPI has a longer organic chain (via introducing extra ethyl groups) than PEPI, thus its inorganic skeleton can be distorted, bringing on structural disorder. The comparative analyses of spectral profiles and temporal dynamics revealed that the greater structural disorder in PBPI results in more defect states serving as trap states to promote exciton dynamics. In addition, the fine-structuring of excitonic resonances was unveiled by temperature-dependent ultrafast spectroscopy, suggesting its correlation with inorganic skeleton rather than organic chain. Moreover, the photoexcited coherent phonons were observed in both PEPI and PBPI, pointing to a subtle impact of structural disorder on the low-frequency Raman-active vibrations of inorganic skeleton. This work provides valuable insights into the optical properties, excitonic behaviors and dynamics, as well as coherent phonon effects in 2D hybrid perovskites.  相似文献   

9.
    
Two-dimensional (2D) materials have become a worldwide hot topic due to their fascinating properties, including high carrier mobility, tunable bandgap, ultra-broadband optical absorption and response. The versatility of 2D materials enable it hold great potential to achieve high performance Terahertz (THz) optoelectronic devices. However, the THz radiation, range from infrared to microwave, known as the THz gap, much less investigated than that of other electromagnetic wave. Motivated by this lack of knowledge, we reviewed the recent advances of research into 2D materials based THz optoelectronic devices. Firstly, we introduced the background and motivation of this review. Then, the suitable 2D material candidates are exhibited, followed by a comprehensive review of their applications in THz generation devices, modulator, THz shielding, and photodetectors. Finally, the challenges and further development directions are concluded. We believe that some milestone investigations of 2D materials based THz optoelectronic devices will emerge soon, which will bring about great industrial revelations in 2D materials-based nanodevice commercialization.  相似文献   

10.
卤化铅钙钛矿纳米晶体(Leadhalideperovskitesnanocrystals,LHPNCs)具有高摩尔吸光度系数、晶格缺陷高容忍度、超高载流子迁移率和窄发射半峰宽等优良特性,其研究在光伏和光电子领域得到了广泛的重视,而LHPNCs优良的光电特性也使之在分析传感领域受到关注。近年来,国内外相继发表了多篇综述文章,包括LHPNCs的合成、提高LHPNCs材料稳定性的方法及其在太阳能电池、LED、激光、光催化等方面的应用。然而,目前LHPNCs在传感领域,特别在电致化学发光(Electrochemiluminescence,ECL)方面的研究和应用,还缺乏比较系统的综述。该文综述了LHPNCs的ECL研究及其应用情况,讨论了LHPNCsECL相关研究中存在的问题和面临的挑战,以期增加读者对LHPNCsECL研究现状和未来发展趋势的了解。  相似文献   

11.
    
The quaternary halide Cs2AgCrCl6 was prepared in the form of dark purple crystals by reaction of CsCl, AgCl, and CrCl3, at 700 °C. It crystallizes in the trigonal Ba2NiTeO6‐type structure [space group R3 m, Z = 6, a = 7.2692(4) Å, c = 36.443(2) Å] belonging to the family of perovskite polytypes containing sequences of hexagonal close‐packed layers. Groups of three face‐sharing octahedra, which are occupied in the sequence Ag–Cr–Ag, are connected through corner‐sharing by Cr‐centered octahedra. The UV/Vis/NIR diffuse reflectance spectrum shows absorptions arising from d–d transitions typical of octahedral Cr3+ complexes, as confirmed by electronic structure calculations. The compound melts at 506 °C. Magnetic measurements revealed simple paramagnetic behavior consistent with the presence of isolated Cr3+ ions.  相似文献   

12.
    
Photoelectrocatalysis studies have emerged tremendous knowledge and experience, which has led to discovery of a number of active materials. Due to complexity of the processes involved, however, development of suitable semiconductor and catalyst for the photoelectrocatalysis still requires a try-and-error approach as different parameters are coherently varied to determine overall performance. This contribution provides insight into the key optoelectronic properties of the semiconductors, such as absorption coefficient, dielectric constant, effective masses, exciton binding energy, and band positions. The combined assessment from theoretical and experimental points of view is reviewed, which may help thorough understanding of the semiconductors and the way to reliably characterize them, and in turn to develop improved photoelectrocatalytic materials.  相似文献   

13.
    
Metal halide perovskite (MHP) nanocrystals (NCs) have shown promising application in photocatalytic CO2 reduction, but their activities are still largely restrained by severe charge recombination and narrow solar spectrum response. Assembly of heterojunctions can be beneficial to the charge separation in MHPs while the assembly process usually brings native interfacial defects, impeding efficient charge separation between two materials. Herein, an in-situ generation strategy was developed to prepare CsPbBr3/WO3 heterojunction, using WO3 nanosheets (NSs) as growing substrate for the growth of CsPbBr3 NCs. The developed CsPbBr3/WO3 heterojunction exhibited a high-quality interface, greatly facilitating charge transfer between two semiconductors. The hybrid photocatalyst displayed an excellent activity toward CO2 reduction, which was about 7-fold higher than pristine CsPbBr3 NCs and 3.5-fold higher than their assembled counterparts. The experimental results and theoretical simulations revealed that a Z-scheme mechanism with a favorable internal electric field was responsible for the good performance of CsPbBr3/WO3 heterojunction. By using O-defective WO3 NSs as a near-infrared (NIR) light absorber, the CsPbBr3/WO3 heterojunction could harvest NIR light and showed an impressive activity toward CO2 reduction. This work demonstrates a new strategy to design MHP-based heterojunctions by synergistically considering the interface quality, charge transfer mode, interfacial electric field, and light response range between two semiconductors.  相似文献   

14.
    
Recently, lead halide‐based perovskites have become one of the hottest topics in photovoltaic research because of their excellent optoelectronic properties. Among them, organic‐inorganic hybrid perovskite solar cells (PSCs) have made very rapid progress with their power conversion efficiency (PCE) now at 23.7 %. However, the intrinsically unstable nature of these materials, particularly to moisture and heat, may be a problem for their long‐term stability. Replacing the fragile organic group with more robust inorganic Cs+ cations forms the cesium lead halide system (CsPbX3, X is halide) as all‐inorganic perovskites which are much more thermally stable and often more stable to other factors. From the first report in 2015 to now, the PCE of CsPbX3‐based PSCs has abruptly increased from 2.9 % to 17.1 % with much enhanced stability. In this Review, we summarize the field up to now, propose solutions in terms of development bottlenecks, and attempt to boost further research in CsPbX3 PSCs.  相似文献   

15.
In this study, we used ytterbium (Yb2+) as a dopant in the CsPbI2Br inorganic perovskite thin film and stabilized its black phase. Here, we varied the Yb2+ doping concentration in the CsPb1?xYbxI2Br (x = 0–0.04) perovskite phase through simple solution method. The optimum concentration of Yb2+ showed improved morphology and crystal growth. The fabricated all-inorganic perovskite solar cells (IPVSCs) having CsPb0.97Yb0.03I2Br-based champion device showed the highest 15.41% power conversion efficiency (PCE) for a small area of 0.09 cm2 and 14.04% PCE for a large area of 1 × 1 cm2 with excellent reproducibility, which is higher than the controlled CsPbI2Br device. Detailed photovoltaic analysis revealed that the PCE, open-circuit voltage (VOC), short circuit current density (JSC) and fill factor (FF) of the final IPVSC device attributed to the suppressed charge recombination, better film quality, and well growth orientation of the perovskite film. Moreover, the champion CsPb0.97Yb0.03I2Br device retains >85% initial efficiency after 280 h under 85 °C thermal annealings. Our results provide a new method to boost the performance of the photovoltaic application.  相似文献   

16.
    
Metal halide perovskites (MHPs), in particular lead-based perovskites, have earned recognized fame in several fields for their outstanding optoelectronic properties, including direct generation of free charge carriers, optimal ambipolar charge carrier transport properties, high absorption coefficient, point-defect tolerance, and compositional versatility. Nowadays, this class of materials represents a real and promising alternative to silicon for photovoltaic technologies. This worthy success led to a growing interest in the exploration of MHPs in other hot research fields, such as solar-driven photocatalytic water splitting towards hydrogen production. Nevertheless, many of these perovskites show air and moisture instability problems that considerably hinder their practical application for photocatalytic water splitting. Moreover, if chemical instability is a problem that can be in part mitigated by the optimization of the chemical composition and crystal structure, the presence of lead represents a real problem for the practical application of MHPs in commercial devices due to environmental and healthcare issues. To successfully overcome these problems, lead-free metal halide perovskites (LFMHPs) have gained increasing interest thanks to their optoelectronic properties, comparable to lead-based materials, and their more eco-friendly nature. Among all the lead-free perovskite alternatives, this mini-review considers bismuth-based perovskites and perovskite derivatives with a specific focus on solar-driven photocatalysis application for H2 evolution. Special attention is dedicated to the structure and composition of the different materials and to the advantage of heterojunction engineering and the relative impact on the photocatalytic process.  相似文献   

17.
采用密度泛函理论和含时密度泛函理论方法计算了2个吩噻嗪类染料及其吸附到TiO2上后分子的基态和激发态光物理性质与热力学参数.结果表明,电子给体的改变虽未明显改变染料的光谱性质(垂直跃迁能和振子强度),但可以改变分子的前线轨道能级,进而影响染料分子的激子结合能Eb及激发态电子注入到半导体TiO2中的驱动力△Gint的大小...  相似文献   

18.
    
Two-dimensional (2D) halide perovskites have recently emerged as a more stable and more versatile family of materials than three-dimensional (3D) perovskite solar cell absorbers. Although solar cells made with 2D perovskites have yet to improve their power conversion efficiencies to compete with 3D perovskite solar cells, their immense diversity offers great opportunities and avenues for research that will likely close the gap between these two. Further, 2D perovskites can have various roles within a solar cell, either as the primary light absorber, as a capping layer, passivating layer, or within a mixed 2D/3D perovskite solar cell absorber. In this Minireview, we will review the history of 2D perovskites in solar cells, the relevant properties of such materials, the different roles that they can play in a solar cell, as well as current trends and challenges.  相似文献   

19.
    
Structural dimensionality and electronic dimensionality play a crucial role in determining the type of excitonic emission in hybrid metal halides (HMHs). It is important but challenging to achieve free exciton (FE) emission in zero-dimensional (0D) HMHs based on the control over the electronic dimensionality. In this work, a quasi-0D HMH (C7H15N2Br)2PbBr4 with localized electronic dimensionality is prepared as a prototype model. With increasing pressure onto (C7H15N2Br)2PbBr4, the broad and weak self-trapped exciton (STE) emission at ambient conditions is considerably enhanced before 3.6 GPa, which originates from more distorted [PbBr4]2− seesaw units upon compression. Notably, a narrow FE emission in (C7H15N2Br)2PbBr4 appears at 3.6 GPa, and then this FE emission is gradually strengthened up to 8.4 GPa. High pressure structural characterizations reveal that anisotropic contraction of (C7H15N2Br)2PbBr4 results in a noticeable reduction in the distance between adjacent [PbBr4]2− seesaw units, as well as an obvious enhancement of crystal stiffness. Consequently, the electronic connectivity in (C7H15N2Br)2PbBr4 is sufficiently promoted above 3.6 GPa, which is also supported with theoretical calculations. The elevation of electronic connectivity and enhanced stiffness together lead to pressure-induced FE emission and subsequent emission enhancement in quasi-0D (C7H15N2Br)2PbBr4.  相似文献   

20.
    
Exciton localization is an approach for preparing highly luminescent semiconductors. However, realizing strongly localized excitonic recombination in low-dimensional materials such as two-dimensional (2D) perovskites remains challenging. Herein, we first propose a simple and efficient Sn2+ vacancy (VSn) tuning strategy to enhance excitonic localization in 2D (OA)2SnI4 (OA=octylammonium) perovskite nanosheets (PNSs), increasing their photoluminescence quantum yield (PLQY) to ≈64 %, which is among the highest values reported for tin iodide perovskites. Combining experimental with first-principles calculation results, we confirm that the significantly increased PLQY of (OA)2SnI4 PNSs is primarily due to self-trapped excitons with highly localized energy states induced by VSn. Moreover, this universal strategy can be applied for improving other 2D Sn-based perovskites, thereby paving a new way to fabricate diverse 2D lead-free perovskites with desirable PL properties.  相似文献   

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