- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Highly oriented perovskites for efficient light-emitting diodes with balanced charge transport
摘要： Ruddlesden-Popper (RP) perovskites have attracted interests due to high performance in perovskite light-emitting diodes (PeLEDs). However, the insulating organic spacers decrease carrier mobility, and increase charge accumulation and non-radiative recombination losses, which significantly undermine device performance. Herein, by blending NH3I(CH2)8NH3I (ODA) and INH3(CH2)2O(CH2)2O(CH2)2NH3I (EDBE) large organic spacers into the precursor solution, we achieve preferential orientation of perovskite crystals perpendicular to the substrate with conductive channels across the two injecting electrodes. Consequently, effective charge injection and balanced charge transport are achieved, which is beneficial to increase radiation recombination. A low turn-on voltage of 1.4 V is achieved for mixture-1.5 perovskite (ODA: EDBE=3:2, molar ratio) PeLEDs, and a maximum external quantum efficiency increases to 5.8% (EL peak ≈766 nm) at 2.0 V with a current density of 6.05 mA cm?2 compared to that of the pure ODA (2.4%) and EDBE (1.1%) devices. The findings may spur new developments in charge injection and electron-hole balance for realizing efficient PeLEDs.
关键词： Perovskites,Ruddlesden-Popper,Organic spacers,Light-emitting diodes,Charge transport
更新于2025-09-12 10:27:22
-
2D Nanoplates and Scaled-up Bulk Polycrystals of Ruddlesden-Popper, Cs2PbI2Cl2 for Optoelectronic Applications
摘要： Two-dimensional (2D) layered Ruddlesden-Popper (RP) phases of halide perovskite offer exotic properties and interesting structure, which make them suitable candidate for solar photovoltaics, light emitting diode (LED) and photodetector applications. Simple and scaled-up synthesis, chemical transformations, doping and stability are the important steps towards the applications. Herein, all-inorganic RP phase of Cs2PbI2Cl2 was synthesized via a facile hot-injection method using benzoyl halides as halide sources. Different morphologies in the form of 2D nanoplates (NPLs) and small nanocrystals (NCs) were obtained by changing the concentration of capping agents (i.e., oleic acid and oleylamine) in solution. The excitonic absorption peak was appeared for NPLs and NCs, which is the characteristic feature of 2D halide perovskites. Further, the scalable quantity (~1 gm) of bulk powder and micron-sized particles of Cs2PbI2Cl2 were synthesized via liquid assisted mechanochemical grinding and anti-solvent method, respectively. We have performed post-synthetic chemical transformation to synthesize three-dimensional (3D) CsPbBr3 disk-shaped particles and zero-dimensional (0D) Cs4PbCl6 NCs from the pre-synthesized RP Cs2PbI2Cl2 NCs in solution and studied their optical properties. Finally, doping of Mn2+ was carried out in Cs2PbI2Cl2 NCs, which demonstrated typical feature of Mn2+ dopant emission along with host emission properties. Low-temperature (77 K) photoluminescence (PL) spectra reveal red-shifted and line-width broadening emission along with longer PL lifetime for both undoped and Mn-doped NCs compared to room temperature PL. Further, the temperature-dependent PL spectra and thermogravimetric analysis (TGA) revealed excellent thermal stability of Cs2PbI2Cl2. This work offers an insight for exploration of synthesis process, post-synthetic chemical transformation and dopant insertion in all-inorganic 2D RP perovskites, which is important step forward for application. Demonstrations of various simple synthesis of both the nano and bulk phases, structural transformation and detailed optical properties of doped and undoped RP perovskite halide nanostructures unfold innovative opportunities for applicability in optoelectronics such as in solar cell and photodetectors.
关键词： Synthesis,2D Halide Perovskites,Post-synthetic Transformation,Optical Properties,Mn-doping,Thermal Stability,Ruddlesden-Popper Phase
更新于2025-09-12 10:27:22
-
Investigation of structural, optical and electrical properties of Sr2SnO4, Sr1.99Eu0.01SnO4 and Sr2Sn0.99Eu0.01O4 Ruddlesden Popper oxide
摘要： Structural, electrical and optical properties of samples have been reported in this paper. The samples with compositions Sr2SnO4, Sr1.99Eu0.01SnO4 and Sr2Sn0.99Eu0.01O4 are prepared by solid state ceramic route followed by calcination at temperature 1000oC for 8 h. Rietveld refinement of powder X-ray diffraction (XRD) data showed tetragonal structure in all samples with space group (I4/mmm). X-ray photoelectron spectroscopy (XPS) studies indicate the presence of Sn in Sn4+ and Sn2+ state in both the samples. The electrical conductivity of the sample follows universal johnscher’s law.“ ?? = ?????? + ?????? ”. Temperature dependent electrical conductivity in samples Sr2SnO4, Sr1.99Eu0.01SnO4 and Sr2Sn0.99Eu0.01O4 with activation energy 0.16, 0.17, 0.16 eV respectively. Conduction in these samples show intense emission peak at 577, 595 and 612 nm assigned to transitions from 5D0?7FJ (J=0, 1, 2, 3) levels of Eu3+. Higher the value of conductivity ??????and integrated area of emission peak for Sr1.99Eu0.01SnO4 is making it more multifunctional than Sr2Sn0.99Eu0.01O4.
关键词： Ghosh scaling,Ruddlesden Popper oxide: Sr2SnO4,Rietveld refinement,Universal Johnscher’s power law
更新于2025-09-11 14:15:04
-
Atomic Structure and Electrical Activity of Grain Boundaries and Ruddlesden-Popper Faults in Cesium Lead Bromide Perovskite
摘要： To evaluate the role of planar defects in lead-halide perovskites—cheap, versatile semiconducting materials—it is critical to examine their structure, including defects, at the atomic scale and develop a detailed understanding of their impact on electronic properties. In this study, postsynthesis nanocrystal fusion, aberration-corrected scanning transmission electron microscopy, and first-principles calculations are combined to study the nature of different planar defects formed in CsPbBr3 nanocrystals. Two types of prevalent planar defects from atomic resolution imaging are observed: previously unreported Br-rich [001](210)∑5 grain boundaries (GBs) and Ruddlesden–Popper (RP) planar faults. The first-principles calculations reveal that neither of these planar faults induce deep defect levels, but their Br-deficient counterparts do. It is found that the ∑5 GB repels electrons and attracts holes, similar to an n–p–n junction, and the RP planar defects repel both electrons and holes, similar to a semiconductor–insulator–semiconductor junction. Finally, the potential applications of these findings and their implications to understand the planar defects in organic–inorganic lead-halide perovskites that have led to solar cells with extremely high photoconversion efficiencies are discussed.
关键词： Ruddlesden–Popper faults,lead-halide perovskites,scanning transmission electron microscopy,density-functional theory,grain boundaries
更新于2025-09-10 09:29:36
-
Phase Intergrowth and Structural Defects in Organic Metal Halide Ruddlesden–Popper Thin Films
摘要： Organic metal halide Ruddlesden?Popper layered perovskite phases combine the excellent optoelectronic properties of three-dimensional, bulk hybrid perovskites with superior material stability under ambient conditions. However, the thin film structure of these layered perovskites is still poorly understood, as phase purity is typically determined solely by specular X-ray diffraction. The thin film structure of these Ruddlesden?Popper phases was examined by increasingly local characterization techniques. From the comparison of grazing-incidence wide-angle X-ray scattering patterns of cast films to expected scattering from single-crystal structures, significant in-plane disorder was observed. Spatially localized photoluminescence measurements show that films do not phase separate on the micrometer scale. Selected area electron diffraction measurements show the intergrowth of different phases within the same thin film, consistent with previous observations seen in epitaxially grown Ruddlesden?Popper complex oxides. Despite the presence of phase impurities that would typically be detrimental for device performance, fits to photothermal deflection spectroscopy measurements show relatively low Urbach energies of 33 meV for (C4H9NH3)2(CH3NH3)2Pb3I10 and 32 meV for (C4H9NH3)2(CH3NH3)3Pb4I13, indicating that the electronic properties are insensitive to the phase impurities.
关键词： phase intergrowth,structural defects,Ruddlesden?Popper,thin films,Organic metal halide,perovskite
更新于2025-09-09 09:28:46
-
Structural and thermodynamic limits of layer thickness in 2D halide perovskites
摘要： In the fast-evolving field of halide perovskite semiconductors, the 2D perovskites (A′)2(A)n?1MnX3n+1 [where A = Cs+, CH3NH3+, HC(NH2)2+; A′ = ammonium cation acting as spacer; M = Ge2+, Sn2+, Pb2+; and X = Cl?, Br?, I?] have recently made a critical entry. The n value defines the thickness of the 2D layers, which controls the optical and electronic properties. The 2D perovskites have demonstrated preliminary optoelectronic device lifetime superior to their 3D counterparts. They have also attracted fundamental interest as solution-processed quantum wells with structural and physical properties tunable via chemical composition, notably by the n value defining the perovskite layer thickness. The higher members (n > 5) have not been documented, and there are important scientific questions underlying fundamental limits for n. To develop and utilize these materials in technology, it is imperative to understand their thermodynamic stability, fundamental synthetic limitations, and the derived structure–function relationships. We report the effective synthesis of the highest iodide n-members yet, namely (CH3(CH2)2NH3)2(CH3NH3)5Pb6I19 (n = 6) and (CH3(CH2)2NH3)2(CH3NH3)6Pb7I22 (n = 7), and confirm the crystal structure with single-crystal X-ray diffraction, and provide indirect evidence for “(CH3(CH2)2NH3)2(CH3NH3)8Pb9I28” (“n = 9”). Direct HCl solution calorimetric measurements show the compounds with n > 7 have unfavorable enthalpies of formation (ΔHf), suggesting the formation of higher homologs to be challenging. Finally, we report preliminary n-dependent solar cell efficiency in the range of 9–12.6% in these higher n-members, highlighting the strong promise of these materials for high-performance devices.
关键词： Ruddlesden–Popper halide perovskites,homologous series,photovoltaics,formation enthalpy,layered compounds
更新于2025-09-04 15:30:14