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Exploring the Carrier Dynamics in Zinc Oxide-Metal Halide Based Perovskites Nanostructures: Towards Reduced Dielectric Loss and Improved Photocurrent
摘要： Metal-halide based perovskites have emerged as a potential candidate for optoelectronic applications due to their impressive performance achieved by tuning the optical/electrical properties through tailoring the perovskite nanostructures. Herein, we report the synthesis of composite nanostructures by incorporation of ZnO (~6 nm) into CsPbBr3 (CPB) perovskite framework, which has significant enhancement of photocurrent, due to efficient interfacial charge separation and reduced dielectric loss. Detailed steady state and time resolved PL studies have been carried out to understand charge transfer dynamics in CsPbBr3/ZnO nanostructure composite system. Femtosecond transient absorption and broadband dielectric spectroscopy studies were carried out to determine the charge carrier relaxation and transfer mechanism. Redox energy level diagram suggests photo-excited electron from conduction band (CB) CPB can be transferred to the CB of ZnO NP due to thermodynamic viability. Ultrafast studies reveal the electron transfer take place from the perovskite nanostructures to ZnO NP within ～500 fs and limits of the recombination process by efficient charge separation and charge accumulation at the interfaces. Dielectric studies also reveal reduced charge leakage in composite nanostructures with efficient charge separation by facilitating the charge accumulation at the interfaces. Overall, the efficient charge transfer and slow carrier recombination with reduced dielectric losses significantly improved the photocurrent behavior CsPbBr3/ZnO nanostructure composite system as desired for optoelectronic devices.
关键词： ZnO,charge transfer dynamics,optoelectronic applications,dielectric loss,photocurrent,Metal-halide based perovskites,CsPbBr3
更新于2025-09-23 15:21:01
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Remote Phononic Effects in Epitaxial Ruddlesden-Popper Halide Perovskites
摘要： Despite their weak nature, van der Waals (vdW) interactions have been shown to effectively control the optoelectronic and vibrational properties of layered materials. However, how vdW effects exist in Ruddlesden-Popper layered halide perovskites remains unclear. Here we reveal the role of interlayer vdW force in Ruddlesden-Popper perovskite in regulating phase transition kinetics and carrier dynamics, based on high-quality epitaxial single crystalline (C4H9NH3)2PbI4 flakes with controlled dimensions. Both substrate-perovskite epitaxial interaction and interlayer vdW interaction play significant roles in suppressing the structural phase transition. With reducing flake thickness from ~100 nm to ~20 nm, electron-phonon coupling strength decreases by ~30%, suggesting the ineffectiveness of phonon confinement of the natural quantum wells. Therefore, the conventional understanding that vdW perovskite is equivalent to a multiple quantum well has to be substantially amended due to significant nonlocal phononic effects in the layered crystal where intralayer interaction is not drastically different from the interlayer force.
关键词： phase transition,electron-phonon coupling,Ruddlesden-Popper perovskites,epitaxial growth,van der Waals interactions
更新于2025-09-23 15:21:01
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Two-dimensional Hybrid Halide Perovskites: Principles and Prom-ises
摘要： Hybrid halide perovskites have become the “next big thing” in emerging semiconductor materials as the past decade witnessed their successful application in high-performance photovoltaics. This resurgence has seen enormous and widespread development of the three-dimensional (3D) perovskites, spearheaded by CH3NH3PbI3. The next generation of halide perovskites, however, is characterized by reduced dimensionality perovskites, emphasizing on the two-dimensional (2D) perovskite derivatives which expand as a more diverse subgroup of semiconducting hybrids that possesses even higher tunability and excellent photophysical properties. In this perspective, we begin with a historical flashback that traces back to early reports before the “perovskite fever” and we follow this original work to its fruition in the present day, where 2D halide perovskites are on the spotlight of current research, thriving on several aspects of high-performance optoelectronics. We approach the evolution of 2D halide perovskites from a structural perspective, providing a classification for the diverse structure-types of the materials, which largely dictate the unusual physical properties observed. We sort out the 2D hybrid halide perovskite based on two key components: the inorganic layers and their modification and the organic cation diversity. As these two heterogeneous components blend, either by synthetic manipulation (shuffling the organic cations or inorganic elements) or by external stimuli (temperature and pressure), the modular perovskite structure evolves to construct crystallographically defined quantum wells (QW). The complex electronic structure that arises is sensitive to the structural features that could be in turn used as a knob to control the dielectric and optical properties the QWs. We conclude this perspective with the most notable optoelectronic device achievements that have been demonstrated to date with an eye towards future material discovery and potential technological developments.
关键词： two-dimensional (2D) perovskite derivatives,optoelectronic devices,quantum wells (QW),Hybrid halide perovskites,semiconducting hybrids
更新于2025-09-23 15:21:01
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Fabrication of bifacial sandwiched heterojunction photoconductor a?? Type and MAI passivated photodiode a?? Type perovskite photodetectors
摘要： In this work, we report novel heterojunctions perovskite photodetector architecture utilizing metal-free contact electrodes. The metal-free contact electrodes were exploited to fabricate photoconductor – type perovskite photodetector. The attempt to investigate the effect of passivating the active layers of the as – proposed architecture with electrolytic MAI gave rise to a photodiode – type perovskite photodetector. These two photodetector types are sensitive and responsive to light sources through their dual transparent electrodes faces (N-face and T-face). We also showed that passivating the surfaces of the sandwiched perovskite layers with MAI solution improves the performance of the fabricated photodetectors, where the detectivity is enhanced by a factor of hundred compared to non-passivated devices. The proposed photodetectors architectures demonstrate champion dual-detectivity (1.77×1014 Jones for N-face and 4.64 × 1014 Jones for T-face), dual-responsivity (1.94 × 103 A/W for N-face and 1.61 × 103 A/W for T-face) and high dual – sensitivity (3.3 × 102 for N-face and 1.1 × 102 for T-face). All these properties were obtained from the two faces of the MAI passivated photodetectors under 0.02 mW/cm2 red LED illumination and at -2.0 bias voltage. This novel architecture may scale up towards building energy and cost efficient classes of optoelectronic and photovoltaic devices which are responsive to light in two directions.
关键词： MAI Passivation,Bifacial,Photoconductor,Perovskites,Photodetectors,Photodiode
更新于2025-09-23 15:21:01
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Superficial-Layer-Enhanced Raman Scattering (SLERS) for Depth Detection of Noncontact Molecules
摘要： Although the strength of Raman signals can be increased by many orders of magnitude on noble metal nanoparticles, this enhancement is confined to an extremely short distance from the Raman-active surface. The key to the development of Raman spectroscopy for applications in diagnosis and detection of cancer and inflammatory diseases, and in pharmacology, relies on the capability of detecting analytes that are noninteractive with Raman-active surfaces. Here, a new Raman enhancement system is constructed, superficial-layer-enhanced Raman scattering (SLERS), by covering elongated tetrahexahedral gold nanoparticle arrays with a superficial perovskite (CH3NH3PbBr3) film. Plasmonic decay is depressed along the vertical direction away from the noble metal surface and the penetration depth is increased in the perovskite media. The vertical penetration of SLERS is verified by the spatial distribution of the analytes via Raman imaging in layer-scanning mode.
关键词： perovskites,self-assembly,Raman imaging,superficial-layer-enhanced Raman scattering
更新于2025-09-23 15:21:01
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Organohalide Lead Perovskites: More Stable than Glass under Gamma-Ray Radiation
摘要： Organohalide metal perovskites have emerged as promising semiconductor materials for use as space solar cells and radiation detectors. However, there is a lack of study of their stability under operational conditions. Here a stability study of perovskite solar cells under gamma-rays and visible light simultaneously is reported. The perovskite active layers are shown to retain 96.8% of their initial power conversion efficiency under continuous irradiation of gamma-rays and light for 1535 h, where gamma-rays have an accumulated dose of 2.3 Mrad. In striking contrast, a glass substrate shows obvious loss of transmittance under the same irradiation conditions. The excellent stability of the perovskite solar cells benefits from the self-healing behavior to recover its efficiency loss from the early degradation induced by gamma-ray irradiation. Defect density characterization reveals that gamma-ray irradiation does not induce electronic trap states. These observations demonstrate the prospects of perovskite materials in applications of radiation detectors and space solar cells.
关键词： gamma-ray radiation,solar cells,self-healing,organohalide perovskites,outer space,stability
更新于2025-09-23 15:21:01
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Cation Exchange as a Mechanism to Engineer Polarity in Layered Perovskites.
摘要： Cation exchange reactions performed on the n = 2 Dion-Jacobson phases RbNdNb2O7 and RbNdTa2O7, using LiNO3 and NaNO3, yield the corresponding LiNdM2O7 and NaNdM2O7 (M = Nb, Ta) phases. Synchrotron X-ray and neutron powder diffraction data, in combination with second-harmonic generation data and supported by first-principles DFT calculations, reveal that the LiNdM2O7 phases adopt n = 2 Ruddlesden-Popper type structures with an aˉaˉc+/-(aˉaˉc+) distortion described in the polar space group B2cm. In contrast, the NaNdM2O7 phases adopt n = 2 Ruddlesden-Popper type structures with an aˉb0c0/b0aˉc0 distortion, described in the centrosymmetric space group P42/mnm. The differing structures adopted by the LiNdM2O7 and NaNdM2O7 phases are rationalized on the basis of a competition between i) optimizing the size of the Li/Na coordination site via octahedral tilting and ii) ordering the Na/Li cations within the (Li/Na)O2 sheets to minimize cation-cation repulsion – the former appears to be the dominant factor for the Li phases and the latter factor dominates for the Na phases. The strong A’-cation dependence of the tilting distortions adopted by the A’NdM2O7 phases suggests that by careful selection of the substituting cation the tilting distortions of layered perovskite phases can be rationally tuned to adopt polar configurations, and thus new ferroelectric phases can be synthesized.
关键词： Layered perovskites,Cation exchange,Structural distortion,Ferroelectric materials,Polarity engineering
更新于2025-09-23 15:21:01
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Estimation of the Rashba Strength from Second Harmonic Generation in 2D and 3D Hybrid Organic-Inorganic Perovskites
摘要： The Rashba e?ect (RE), caused by concurrent spin-orbit coupling and structural inversion asymmetry (SIA), has been invoked to explain outstanding optoelectronic properties of hybrid organic inorganic perovskites (HOIPs). The SIA in HOIPs also manifests itself in second harmonic generation (SHG). Here we establish a quantitative relation between the RE strength and the low-frequency SHG value in 2D and 3D HOIPs using a newly developed e?ective-mass model. The calculated SHG, which exhibits one- and two-photon resonances between the valence and conduction bands, approaches a ?nite value at low frequencies. Using the measured SHG values in literature, the estimated RE strength is 10?3 eV?A for 3D CH3NH3PbI3 and 4 × 10?2 eV?A for 2D (C4H9NH3)2PbI4. Our results facilitate a simple and reliable determination of the RE strength of 2D and 3D HOIPs and help quantify the impact of RE on various properties in HOIPs.
关键词： second harmonic generation,Rashba effect,hybrid organic-inorganic perovskites,structural inversion asymmetry,spin-orbit coupling
更新于2025-09-23 15:21:01
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Promoting Photocatalytic H <sub/>2</sub> Evolution on Organic–Inorganic Hybrid Perovskite Nanocrystals by Simultaneous Dual-Charge Transportation Modulation
摘要： Organic-inorganic hybrid perovskites have demonstrated great potential in solar cells fabrication due to the excellent optoelectronic properties. However, their success in solar cells has been hardly translated to producing solar fuels due to the instability issue and serious charge recombination at the nanoscale domain. Herein, we show for the first time that organic-inorganic hybrid perovskite methylammonium lead bromide (MAPbBr3) nanocrystals can be stabilized in aqueous HBr solution and achieve photocatalytic H2 production reaction under visible light. More impressively, by hybridizing MAPbBr3 with Pt/Ta2O5 and poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) nanoparticles as electron and hole transporting motifs, respectively, drastically enhanced charge transportation on MAPbBr3 together with improved catalysis were achieved. As a consequence, the rate of photocatalytic hydrogen evolution on pristine MAPbBr3 was increased by ca. 52 times by introducing dual nanoscale charge transporting highways, achieving an apparent quantum efficiency of ca. 16.4% for H2 evolution at 420 nm.
关键词： Organic-inorganic hybrid perovskites,photocatalytic H2 evolution,visible light,charge transportation,MAPbBr3 nanocrystals
更新于2025-09-23 15:21:01
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Amplified and Multicolor Emission from Films and Interfacial Layers of Lead Halide Perovskite Nanocrystals
摘要： Lead halide perovskites are promising for energy harvesting and lighting applications. We show amplified emission from films of organic-inorganic or all inorganic lead halide perovskite nanocrystals. Also, multicolor emission is detected from interfacial layers of chloride and bromide perovskites. While amplified emission originates from spatial confinement of manifold charge carriers in films, multicolor emission emanates from interfacial ion exchanged layers. In a film, the amplified emission is averaged over a large number of nanocrystals, which prevents us from detecting any spectral narrowing. Conversely, amplified spontaneous emission (ASE) and spectral narrowing are detected from an isolated perovskite microcrystal. Interestingly, under low intensity excitation, a perovskite nanocrystal film shows unusually delayed emission, which becomes extremely fast and spatially confined at higher intensities of excitation light. By precisely detecting photoluminescence from an irradiated area and outside, we reveal the migration as well as confinement of photogenerated charge carriers in the film. The migration of charge carriers is more efficient in a film of organic-inorganic perovskites than all-inorganic perovskites.
关键词： spatial confinement,multicolor emission,interfacial ion exchange,amplified emission,Lead halide perovskites,charge carriers
更新于2025-09-23 15:21:01