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Resolving spatial and energetic distributions of trap states in metal halide perovskite solar cells
摘要： We report the profiling of spatial and energetic distributions of trap states in metal halide perovskite single-crystalline and polycrystalline solar cells. The trap densities in single crystals varied by five orders of magnitude, with a lowest value of 2 × 1011 per cubic centimeter and most of the deep traps located at crystal surfaces. The charge trap densities of all depths of the interfaces of the polycrystalline films were one to two orders of magnitude greater than that of the film interior, and the trap density at the film interior was still two to three orders of magnitude greater than that in high-quality single crystals. Suprisingly, after surface passivation, most deep traps were detected near the interface of perovskites and hole transport layers, where a large density of nanocrystals were embedded, limiting the efficiency of solar cells.
关键词： spatial distribution,solar cells,metal halide perovskite,energetic distribution,trap states
更新于2025-09-23 15:19:57
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Controllable synthesis of all inorganic lead halide perovskite nanocrystals and white light-emitting diodes based on CsPbBr3 nanocrystals
摘要： The colloidal cesium lead halide perovskite nanocrystals (NCs) have attracted much attention over the past five years as a promising class of material with potential application in wide-color-gamut backlight display because of their high photoluminescence quantum yield (PLQY) and narrow-band emission (full-width at half-maximum, FWHM < 35 nm). To controllably synthesize perovskite NCs, the effects of reaction temperature and reaction time on structure, morphology, particle size and photoluminescence (PL) properties of the NCs were systematically investigated in this article. Based on these results, the formation kinetics of the perovskite NCs was analyzed and disclosed in further. Finally, a white light-emitting diode (WLED) was prepared by using synthesized CsPbBr3 NCs and K2SiF6:Mn4+ phosphors as the color converters. The WLED exhibits the bright white emission with a CIE chromaticity coordinate of (0.389, 0.376) and a wide color gamut of 123% of NTSC, indicating a potential application in the field of wide color gamut displays in the future.
关键词： Cesium lead halide perovskite,white light-emitting diodes,photoluminescent,hot-injection method,nanocrystals
更新于2025-09-23 15:19:57
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Influence of Charge Transport Layers on Capacitance Measured in Halide Perovskite Solar Cells
摘要： We show that capacitance-based techniques cannot be used to reliably analyze the properties of defects in the perovskite layer or at its interface due to the influence of hole-transport materials. For hole-transport-layer-free PSCs, high-frequency capacitance can be considered as the geometric capacitance for calculating the dielectric constant of the perovskite layer. We further show that the low-frequency capacitance signature can be used to calculate the activation energy of the ionic conductivity of the perovskite layer.
关键词： Halide perovskite solar cells,Dielectric constant,Hole-transport layer,Capacitance-based techniques,Ionic conductivity
更新于2025-09-23 15:19:57
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Quantum size effect and surface defect passivation in size-controlled CsPbBr3 quantum dots
摘要： Luminescent CsPbBr3 quantum dots (QDs) with adjustable size and bandgap were grown by controlling the synthesis temperature in this paper. As the synthesis temperature increases, the QD size becomes larger and then smaller. The corresponding absorption and steady-state photoluminescence spectrum indicate that the QD band gap becomes smaller and then larger, which is a typical quantum confinement effect. Time-resolved photoluminescence spectrum and femtosecond transient absorption spectrum (fs-TAS) show that the non-radiative recombination probability of photocarriers in small QDs is small it has few defects, indicating that the ligand molecules adsorbed on the surface of QDs effectively passivate the surface defects of CsPbBr3. Finally, the hot-phonon bottleneck effect of CsPbBr3 QDs is revealed by the kinetic curves fitting of fs-TAS and the cooling kinetic process of hot carriers is also discussed in detail. This work provides new insights on size-dependent photophysical properties of CsPbBr3 QDs.
关键词： Quantum confinement effect,Metal halide perovskite QDs,Defect passivation,Hot carriers
更新于2025-09-23 15:19:57
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Tailoring optoelectronic properties of CH3NH3PbI3 perovskite photovoltaics using al nanoparticle modified PC61BM layer
摘要： In photovoltaics, light harvesting is one of the critical factors for the enhancement of power conversion efficiency (PCE). Photon harvesting can be carried out by various methods in perovskite photovoltaic. The improved light harvesting can also be achieved by trapping the light by incorporating metallic nanoparticles at the interface or in the perovskite active layer itself. Either light is absorbed or scattered by metallic nanoparticles depending on the particle size. When light is absorbed by the nanoparticles (size < 20 nm), it behaves like a sub-wavelength antenna due to localized surface plasmon resonance (LSPR) excitation and hence near field effect of plasmonic particle will be interacting to CH3NH3PbI3 active layer. Larger particles (> 20 nm) act as sub-wavelength scattering centers of light and help in trapping incident light. In order to make use of dual effect poly-dispersed spherical aluminium nanoparticles (AlNPs) (size – 20–70 nm) were incorporated in the CH3NH3PbI3 perovskite solar cell at the PC61BM/Al electrode interface. As a result, there is an increase in the optical absorption in the AlNPs embedded device. A detailed study of optical absorption, absorbed light emission characteristics charge trap density and carrier concentration studies, photovoltaic property measurements indicates, improvement in power conversion efficiency arise due to enhancement in JSC. Evaluated device properties indicate that enhancement in JSC arises due to improvement in the active layer photon absorption by both scattering and plasmonic effect in addition to reduced series resistance.
关键词： Trap states,Organic-inorganic halide perovskite solar cell,Ultraviolet plasmonic resonance,Plasmonic nanoparticle current density,Metal nanoparticles
更新于2025-09-23 15:19:57
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Lead-free all-inorganic cesium tin iodide perovskite for filamentary and interface-type resistive switching toward environment-friendly and temperature-tolerant nonvolatile memories
摘要： Recently, organometallic and all-inorganic halide perovskites (HPs) have become promising materials for resistive switching (RS) nonvolatile memory devices with low-power consumption, because they show current–voltage hysteresis caused by fast ion migration. However, the toxicity and environmental pollution potential of lead, a common constituent of HPs, has limited commercial applications of HP-based devices. Here, RS memory devices based on lead-free all-inorganic cesium tin iodide (CsSnI3) perovskites with temperature-tolerance are successfully fabricated. The devices exhibit reproducible and reliable bipolar RS characteristics in both Ag and Au top electrodes (TEs) with different switching mechanisms. The Ag TE devices show filamentary RS behavior with ultra-low operating voltages (< 0.15 V). In contrast, the Au TE devices have interface-type RS behavior with gradual resistance changes. This suggests that the RS characteristics are attributed to either the formation of metal filaments or the ion migration of defects in HPs under applied electric fields. These distinct mechanisms may permit the opportunity to design devices for specific purposes. This work will pave the way for lead-free all-inorganic HP-based nonvolatile memory for commercial applications of HP-based devices.
关键词： valence change mechanism,electrochemically metallization,all-inorganic halide perovskite,lead-free halide perovskite,resistive switching memory
更新于2025-09-19 17:15:36
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Electronic Traps and its Correlations to Perovskite Solar-Cell Performance via Compositional and Thermal-Annealing Controls
摘要： Herein, underlying factors for enabling efficient and stable performance of perovskite solar cells are studied through nanostructural controls of organic-inorganic halide perovskites. Namely, MAPbI3, (FA0.83MA0.17)Pb(I0.83Br0.17)3, and (Cs0.10FA0.75MA0.15)Pb(I0.85Br0.15)3 perovskites (abbreviated as MA, FAMA, and CsFAMA, respectively) are examined with a grain growth control through thermal annealing. FAMA- and CsFAMA- based cells result in stable photovoltaic performance while MA cells are sensitively dependent on the perovskite grain size dominated by annealing time. Micro-/nanoscopic features are comprehensively analysed to unravel the origin that is directly correlated to the cell performance with the applications of electronic-trap characterizations such as photoconductive noise microscopy and capacitance analyses. It is revealed that CsFAMA has a lower trap density compared to MA and FAMA through the analyses of 1/f noises and trapping/detrapping capacitances. Also, an open-circuit voltage (Voc) change is correlated to the variation of trap states during the shelf-life test: FAMA and CsFAMA cells with the negligible change of Voc over weeks exhibit trap states shifting toward the bandedge, although the power-conversion efficiencies are clearly reduced. It is discussed about the origins that critically affect the solar cell performance through the characterizations of shallow/deep traps with additional mobile defects in the perovskite and interfaces.
关键词： 1/f noise,Organic-inorganic halide perovskite,Perovskite solar cell,Capacitance,Electronic trap
更新于2025-09-19 17:15:36
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Exploring the surface chemistry of cesium lead halide perovskite nanocrystals
摘要： Colloidal nanocrystals (NCs) of cesium lead halide perovskites (CsPbX3, X = Cl, Br or I) are emerging as an exciting class of optoelectronic materials, but the retention of their colloidal and structural integrity during isolation, purification and handling still represents a critical issue. The impelling questions concerning their intrinsic chemical instability are connected to the dynamic nature of the bonding between the inorganic surface and the long-chain capping ligands. However, the key aspects of CsPbX3's surface chemistry that directly impact their stability remain elusive. In this contribution, we provide an in-depth investigation of the surface properties of differently composed CsPbX3 NCs, prepared by traditional hot-injection methods. The study, mainly relying on solution NMR spectroscopy, is backed up by elemental analysis as well as morphological, structural and optical investigations. We ascertained that the nature of the ligand adsorption/desorption processes at the NC surface is dependent on its elemental composition, thus explaining the origin of the instability afflicting CsPbI3 NCs. We also evaluated the effect of NC purification as well as of the degradation pathways involving the organic shell on the surface chemistry of CsPbX3 NCs. This study paves the way for new post-functionalization strategies for this promising class of nanomaterials.
关键词： surface chemistry,colloidal stability,degradation pathways,cesium lead halide perovskite nanocrystals,purification,ligand adsorption/desorption,NMR spectroscopy
更新于2025-09-19 17:15:36
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Embedded two dimensional perovskite nanoplatelets with air-stable luminescence
摘要： Two-dimensional (2D) perovskites represent a class of promising nanostructures for optoelectronic applications owing to their giant oscillator strength transition of excitons and high luminescence. However, major challenges lie in the surface ligand engineering and ambient stability. Here we show that air-stable quasi-2D CsPbBr3 nanoplatelets (NPLs) can be formed in the matrix of Cs4PbBr6 nanosheets by reducing the thickness of Cs4PbBr6 to ~7.6 nm, the scale comparable to the exciton Bohr radius of CsPbBr3. The 2D behavior of excitons is evidenced by the linear increase of radiative lifetime with increasing temperature. Moreover, the wide bandgap Cs4PbBr6 plays roles of surface passivation and protection, which leads to good photoluminescence properties without photo-bleaching effect and with ambient stability for over one month. Our work demonstrates a unique quasi-2D heterostructure of perovskite nanomaterials which may either serve as a workbench for studying the exciton recombination dynamics or find application in high performance optoelectronic devices.
关键词： two dimensional exciton,heterostructure,luminescence,lead halide perovskite
更新于2025-09-19 17:15:36
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Cesium Lead Halide Perovskite Nanocrystals Prepared by Anion-exchange for Light-Emitting Diodes
摘要： Cesium lead halide perovskite nanocrystals (NCs) have emerged as a promising emitter for lighting and display technologies. However, the iodide containing CsPb(Br/I)3 and CsPbI3 NCs suffer from chemical and phase degradation to non-functional orthorhombic (δ) phase. To address this challenge, we developed a facile synthetic protocol for halide exchange in pristine CsPbBr3 NCs. The protocol involves change in the nucleophilicity (or basicity) of the halide ions in aqueous-organic media which acts as the driving force to facilitate the halide exchange. Our method avoids the use of additives for anion solubilization, which otherwise induces chemical instability and quench the emission. The halide exchanged CsPb(Br/I)3 and CsPbI3 NCs showed enhanced structural and optical properties, such as high phase stability and emission quantum yields up to 94.2% as compared to the NCs (of same composition) obtained from direct synthesis. In addition, we demonstrated fabrication of light emitting devices (LED) based on halide exchanged CsPb(Br/I)3 and CsPbI3 NCs. The devices showed peak external quantum efficiency (EQE) of 1.9% with a peak wavelength of 670 nm and low luminance turn-on voltage of 2.5 V.
关键词： Lead halide Perovskite,Halide exchange,Quantum dots,Nanocrystals,LED
更新于2025-09-19 17:13:59