Search Results (401)

Lead halide perovskite quantum dots, also known as perovskite nanocrystals, are considered one of the most promising photovoltaic materials for solar cells due to their outstanding optoelectronic properties and simple preparation techniques. The key factors restricting the photoelectric conversion efficiency of solar cell systems are the separation and transmission performances of charge carriers. Here, femtosecond time-resolved ultrafast spectroscopy was used to measure the interfacial charge transfer dynamics of different sizes of CsPbBr₃ assembled with TiO₂. The effect of perovskite size on the charge transfer is discussed. According to our experimental data analysis, the time constants of the interfacial electron transfer and charge recombination of the assembled systems of CsPbBr₃ and titanium dioxide become larger when the size of the CsPbBr₃ nanocrystals increases. We discuss the physical mechanism by which the size of perovskites affects the rate of charge transfer in detail. We expect that our experimental results provide experimental support for the application of novel quantum dots for solar cell materials. Full article

Y₅F₃[AsO₃]₄ crystallizes needle-shaped in the tetragonal space group P4/ncc with the lattice parameters a = 1143.80(8) pm, c = 1078.41(7) pm and c/a = 0.9428 for Z = 4. The yttrium-fluoride substructure linked via secondary contacts forms a three-dimensional network $\begin{array}{c}3\\ \infty \end{array}${[Y₅F₃]¹²⁺} and the remaining part consists of ψ¹-tetrahedral [AsO₃]³⁻ units, which leave lone-pair channels along [001]. In contrast, platelet-shaped Y₅Cl₃[AsO₃]₄ crystals adopt the monoclinic space group C2/c with the lattice parameters a = 1860.56(9) pm, b = 536.27(3) pm, c = 1639.04(8) pm and β = 105.739(3)° for Z = 4. Condensation of [(Y1,2)O₈]¹³⁻ polyhedra via four common edges each leads to fluorite-like $\begin{array}{c}2\\ \infty \end{array}$ {[(Y1,2)O $\begin{array}{c}e\\ 8/2\end{array}$ ]⁵⁻} layers spreading out parallel to the (100) plane. Their three-dimensional linkage occurs via the (Y3)³⁺ cations with their Cl⁻ ligands on the one hand and the As³⁺ cations with their lone-pairs of electrons on the other, which also form within [AsO₃]³⁻ anions lone-pair channels along [010]. Both colorless compounds can be obtained by solid-state reactions from corresponding mixtures of the binaries (Y₂O₃, As₂O₃ and YX₃ with X = F and Cl) at elevated temperatures of 825 °C, most advantageously under halide-flux assistance (CsBr for Y₅F₃[AsO₃]₄ and ZnCl₂ for Y₅Cl₃[AsO₃]₄). By replacing a few percent of YX₃ with EuX₃ or TbX₃, Eu³⁺- or Tb³⁺-doped samples are accessible, which show red or green luminescence upon excitation with ultraviolet radiation. Full article

Mn²⁺ doped metal halide that can be grown by a facile solution reaction is a promising low-cost afterglow material. However, the afterglow mechanism is still elusive. Using a facile method to modulate afterglow time is still to be explored. In this work, we reveal that the afterglow of Cs₂Na_0.2Ag_0.8InCl₆:y%Mn can be significantly modulated by Mn²⁺ concentration. We propose that replacing Ag⁺ with Mn²⁺ leads to the appearance of interstitial Ag⁺, which temporally store the photogenerated electrons (${\mathrm{A}\mathrm{g}}^{+}+{\mathrm{e}}^{-}\to \mathrm{A}\mathrm{g}$). After the removal of excitation, the gradual recombination between residual holes and stored electrons [${\mathrm{h}}^{+}+\left({\mathrm{A}\mathrm{g}}^{+}+{\mathrm{e}}^{-}\right)\to \mathrm{h}\mathsf{\nu }+{\mathrm{A}\mathrm{g}}^{+}$] explains the afterglow. However, excessive Mn²⁺ doping at interstitial sites does not bring about more interstitial Ag⁺ but instead introduces nonradiative traps. Therefore, as the Mn²⁺ concentration increases, the afterglow time increases from 350 s to 530 s and then decreases to 230 s, reaching a maximum at y = 40. Thus, a dynamic optical information storage and encryption application is demonstrated based on the modulated afterglow time. Full article

The rapid growth of the private space industry has intensified the demand for lightweight, efficient, and cost-effective photovoltaic technologies. Metal halide perovskite solar cells (PSCs) offer high power conversion efficiency (PCE), mechanical flexibility, and low-temperature solution processability, making them strong candidates for next-generation space power systems. However, exposure to extreme thermal cycling, high-energy radiation, vacuum, and ultraviolet light in space leads to severe degradation. This study addresses these challenges by introducing three key design strategies: self-healing perovskite compositions that recover from radiation-induced damage, gradient buffer layers that mitigate mechanical stress caused by thermal expansion mismatch, and advanced encapsulation that serves as a multifunctional barrier against space environmental stressors. These approaches enhance device resilience and operational stability in space. The design strategies discussed in this review are expected to support long-term power generation for low-cost satellites, high-altitude platforms, and deep-space missions. Additionally, insights gained from this research are applicable to terrestrial environments with high radiation or temperature extremes. Perovskite solar cells represent a transformative solution for space photovoltaics, offering a pathway toward scalable, flexible, and radiation-tolerant energy systems. Full article

Two-dimensional lead halide perovskites are of significant interest for a variety of practical applications. However, the relationships between their composition and properties are not fully clear. Here we investigated photoluminescence from 2D Ruddlesden–Popper perovskites with different bulky spacer cations. Significant differences in their optical properties and stability are observed, and perovskites with benzylammonium (BZA) and phenethylammonium (PEA) were selected for more detailed investigation of the observed stability differences due to their similar structure. We find that PEA₂PbI₄ exhibits more narrow emission and increased stability compared to BZA₂PbI₄. In addition, PEA₂PbI₄ exhibits self-healing of defects evident from PL enhancement, which is absent for BZA₂PbI₄. The observed differences between perovskites with BZA and PEA spacer cations can be attributed to differences in the formation of spacer cation vacancies. Full article

Two−dimensional halide perovskites have emerged as promising optoelectronic materials, yet the uncontrolled defect formation during synthesis remains a critical challenge for their practical applications. In this work, we systematically investigate the structural, electronic, and optical properties of monolayer CsPb₂Br₅ in two representative configurations: ds−CsPb₂Br₅ and ss−CsPb₂Br₅. By introducing four types of vacancy defects—V_Br−c, V_Br−b, V_Cs, and V_Pb, we analyze their structural distortions, formation energies, and their impact on band structure and optical response using first−principles calculations. Our results reveal that Br−related vacancies are energetically most favorable and induce shallow defect levels and absorption edge redshifts in the ds−CsPb₂Br₅ structure, while in the ss−CsPb₂Br₅ configuration, only V_Br−b forms a defect state. V_Pb and V_Cs lead to significant sub−bandgap absorption enhancement and dielectric response due to band−edge reorganization, despite not introducing in−gap states. Notably, V_Br−c exhibits distinct infrared absorption in the ss−CsPb₂Br₅ model without electronic trap formation. These findings underscore the critical influence of defect type and slab asymmetry on the optoelectronic behavior of CsPb₂Br₅, providing guidance for defect engineering in perovskite−based optoelectronic applications. Full article

Ionic liquids (ILs) can ideally reduce defects and improve the film stability of emissive metal halide perovskite films. In this work, we measure how the structure and emission of methylammonium lead tribromide (MAPbBr₃) perovskite films is modulated by long alkyl chain-containing pyridinium, imidazolium, or pyrrolidinium ILs. Two different film deposition methods are compared, with the resultant films characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and photoluminescence (PL) spectroscopy. For the latter, the differences in PL intensity of the perovskite are quantified using photoluminescence quantum efficiency (PLQE) measurements. It is found that a spin coating method in conjunction with the use of an imidazolium-containing IL (for a given precursor concentration) produces the strongest emissive perovskite. This optimal enhancement is attributed to a function of accessible surface charges associated with the heterocyclic cation of a given IL and perovskite defect passivation by bromide, the latter elucidated with the help of density functional theory. Proof-of-concept device fabrication is demonstrated for the case of a light emitting diode (LED) with the IL present in the emissive perovskite layer. Full article

Metal halide perovskite (MHP) nanocrystals (NCs) offer great potential for high-efficiency optoelectronic devices; however, they suffer from structural softness and chemical instability. Doping MHP NCs can overcome this issue. In this work, we synthesize Mn-doped methylammonium lead bromide (MAPbBr₃) NCs using the ligand-assisted reprecipitation method and investigate their structural and optical stability. X-ray diffraction confirms Mn²⁺ substitution at Pb²⁺ sites and lattice contraction. Photoluminescence (PL) measurements show a blue shift, significant PL quantum yield enhancement, reaching 72% at 17% Mn²⁺ doping, and a 34% increase compared to undoped samples, attributed to effective defect passivation and reduced non-radiative recombination, supported by time-resolved PL data. Mn²⁺ doping also improves long-term stability under ambient conditions. Low-temperature PL reveals the crystal-phase transitions of perovskite NCs and Mn-doped NCs to be somewhat different than those of pure MAPbBr₃. Mn²⁺ incorporation into perovskite promotes self-assembly into superlattices with larger crystal sizes, better structural order, and stronger inter-NC coupling. These results demonstrate that Mn²⁺ doping enhances both optical performance and structural robustness, advancing the potential of MAPbBr₃ NCs for stable optoelectronic applications. Full article

Lead halide perovskites (LHPs) have superior luminescent properties, but their toxicity hinders their commercialization, arousing interests in tin halide perovskites as environmentally friendly substitutes for LHPs. Herein, we synthesized a series of two-dimensional tin halide perovskite ODASnBr_4-xI_x (ODA denotes 1,8-octanediammonium, X = 0, 1, 2, 3, 4) microcrystals via an aqueous-phase method. The differences between ODASnI₄ and ODASnBr₄ in luminescent properties and morphological characteristics were systematically discussed for the first time and attributed to light-driven ligand-to-metal charge transfer. The prepared ODASnBr₄ has a PL peak at 567 nm and a PL QY of 99%, and the white light-emitting diodes fabricated with ODASnBr₄ and commercial blue phosphors realized a luminous efficacy of up to 96.27 lm/W, which demonstrated the remarkable potential of ODASnBr₄ microcrystals for high-efficiency white light-emitting diode applications. Full article

Single-phase white-light-emitting materials, particularly 2D hybrid organic–inorganic halide perovskites, have garnered significant attention due to their strong electron–phonon interactions, which lead to broad luminescence and a notable Stokes shift resulting from self-trapped exciton recombination. However, 2D lead iodide perovskites typically display these characteristics poorly, restricting their efficiency as white-light emitters. This study presents a 2D lead iodide perovskite that incorporates a fluorinated π-conjugated aggregation-induced enhanced emission luminophore, FPCSA, as a bulky organic cation to create a quasi-2D perovskite. The FPCSA cation establishes a Type II energy level alignment with the lead iodide layer in the 2D perovskite, and a significant energy offset effectively suppresses charge transfer, enabling independent emission from both the organic and inorganic layers while facilitating self-trapped exciton formation. Under 315 nm UV excitation, this material demonstrates warm white-light emission with RGB triple-band photoluminescence stemming from the electronically decoupled FPCSA and perovskite layers. These findings provide a promising new method for designing efficient single-phase white-light-emitting materials for optoelectronic applications. Full article

Coupling organic light-harvesting materials with lead halide perovskite quantum dots (LHP QDs) is an attractive approach that could provide great potential in optoelectronic applications owing to the diversity of organic materials available and the intriguing optical and electronic properties of LHP QDs. Here, we demonstrate energy collection by CsPbI₃ QDs from a near-infrared (NIR) light-harvesting upconversion system. The upconversion system consists of Pd-tetrakis-5,10,15,20-(p-methoxycarbonylphenyl)-tetraanthraporphyrin (PdTAP) as the sensitizer to harvest NIR photons and rubrene as the annihilator to generate upconverted photons via triplet fusion. Steady-state and time-resolved photoluminescence spectra reveal that CsPbI₃ QDs are energized via radiative energy transfer from the singlet excited rubrene with photophysics fidelity of respective components. In addition, a volumetric display demo incorporating CsPbI₃ QDs as light emitters employing triplet fusion upconversion was developed, showing bright luminescent images from CsPbI₃ QDs. These results present the feasibility of integrating organic light-harvesting systems and perovskite QDs, enabling diverse light harvesting and activation of perovskite materials for optoelectronic applications. Full article

Using reduced-dimensional halide perovskites is emerging as a promising strategy for enhancing the stability of optoelectronic devices such as solar cells, even if their performances remain a step below those of the 3D halide perovskites. Two-dimensional Ruddlesden–Popper (2D-RP) structures are characterized by the n parameter that represents the number of PbI₆ layers in the spacer-separated perovskite slabs. The present study focuses on formamidinium (FA)-based 2D-RP type perovskites denoted as PMA₂FA_n−1Pb_nI_3n+1 (PMA = Phenylmethylammonium or benzylammonium). We investigate the effect of n on the one step growth mechanism and the film morphology, microstructure, phase purity, and optoelectronic properties. Our findings demonstrate that the average n is not only determined by the initial spacer content in the precursor solution but also by the thermal annealing process that leads to a partial spacer loss. Depending on n, perovskite solar cells achieving a power conversion efficiency up to 21%, coupled with enhanced film stability compared to 3D perovskites have been prepared. By using MACl additive and an excess of PbI₂ in the perovskite precursor solution, we have been able to achieve high efficiency and to stabilize the n = 5 perovskite solar cells. This research represents a significant stride in comprehending the formation of FA-based layered perovskites through one-step sequential deposition, enabling control over their phase distribution, composition, and orientation. Full article

All-perovskite tandem solar cells (APTSCs) offer a promising pathway to surpassing the efficiency limits of single-junction photovoltaics. The wide-bandgap (WBG) subcell, serving as the top absorber, plays a critical role in optimizing light harvesting and charge extraction in tandem architectures. This review comprehensively summarizes recent advancements in WBG subcells, focusing on material design, defect passivation strategies, and interfacial engineering to address challenges such as phase instability, halide segregation, and voltage losses. Key innovations, including compositional tuning, additive engineering, and charge transport layer optimization, are critically analyzed for their contributions to efficiency and stability enhancement. Despite significant progress, challenges remain regarding scalability, long-term stability under illumination, and cost-effective fabrication. Future research directions include the development of lead-reduced perovskites, machine learning-guided material discovery, and scalable deposition techniques. This review provides insights into advancing WBG subcells toward high-efficiency, stable, and eco-friendly APTSCs for next-generation solar energy applications. Full article

The persistent operational instability of all-inorganic cesium lead halide (CsPbX₃) perovskite nanocrystals (NCs) has hindered their integration into white-light-emitting diodes (WLEDs). This study introduces a transformative approach by engineering a phase transition from CsPbBr₃ NCs to zirconium bromide (ZrBr₄)-stabilized hexagonal nanocomposites (HNs) through a modified hot-injection synthesis. Structural analyses revealed that the ZrBr₄-mediated phase transformation induced a structurally ordered lattice with minimized defects, significantly enhancing charge carrier confinement and radiative recombination efficiency. The resulting HNs achieved an exceptional photoluminescence quantum yield (PLQY) of 92%, prolonged emission lifetimes, and suppressed nonradiative decay, attributed to effective surface passivation. The WLEDs with HNs enabled a breakthrough luminous efficiency of 158 lm/W and a record color rendering index (CRI) of 98, outperforming conventional CsPbX₃-based devices. The WLEDs exhibited robust thermal stability, retaining over 80% of initial emission intensity at 100 °C, and demonstrated exceptional operational stability with negligible PL degradation during 50 h of continuous operation at 100 mA. Commission Internationale de l’Éclairage (CIE) coordinates of (0.35, 0.32) validated pure white-light emission with high chromatic fidelity. This work establishes ZrBr₄-mediated HNs as a paradigm-shifting material platform, addressing critical stability and efficiency challenges in perovskite optoelectronics and paving the way for next-generation, high-performance lighting solutions. Full article

Semiconductor photonic nanowires are critical components for nanoscale light manipulation in integrated photonic and electronic devices. Optimizing their optical performance requires enhanced photon conversion efficiency, for which a promising solution is to combine semiconductors with noble metals, using the surface plasmon resonance of noble metals to enhance the photon absorption efficiency. Here, we report plasmon-enhanced light emission in a hybrid nanowire device composed of perovskite semiconductor nanowires and silver nanoparticles formed using superfluid helium droplets. A cesium lead halide perovskite-based four-layer structure (CsPbBr₃/PMMA/Ag/Si) effectively reduces the metal’s plasmonic losses while ensuring efficient surface plasmon–photon coupling at moderate power. Microphotoluminescence and time-resolved spectroscopy techniques are used to investigate the optical properties and emission dynamics of carriers and excitons within the hybrid device. Our results demonstrate an intensity enhancement factor of 29 compared with pure semiconductor structures at 4 K, along with enhanced carrier recombination dynamics due to plasmonic interactions between silver nanoparticles and perovskite nanowires. This work advances existing approaches for exciting photonic nanowires at low photon densities, with potential applications in optimizing single-photon excitations and emissions for quantum information processing. Full article