Hybrid Lead Halide Research Articles

Bulk Mn2+ Doped 1D Hybrid Lead Halide Perovskite with Highly Efficient, Tunable and Stable Broadband Light Emissions.

Mn2+ doped colloidal three-dimensional (3D) lead halide perovskite nanocrystal (PNC) has attracted intensive research attention; however, the low exciton binding energy and fatal optical instability of 3D PNC seriously hinder the optoelectronic application. Therefore, it remains significant to explore new stable host perovskite with strongly bound exciton to realize more desirable luminescent property. In this work, we utilized bulk one-dimensional (1D) hybrid perovskite of [AEP]PbBr5 ⋅ H2 O (AEP=N-aminoethylpiperazine) as structural platform to rationally optimize the luminescent property by a controllable Mn2+ doping strategy. Significantly, the series of Mn2+ -doped 1D [AEP]PbBr5 ⋅ H2 O show enhanced energy transfer efficiency from the strongly bound excitons of host material to 3d electrons of Mn2+ ions, resulting in tunable broadband light emissions from weak yellow to strong red spectral range with highest photoluminescence quantum yield up to 28.41 %. More importantly, these Mn2+ -doped 1D perovskites display ultrahigh structural and optical stabilities in humid atmosphere, water and high temperature exceeding the conventional 3D PNC. Combined highly efficient, tunable and stable broadband light emissions enable Mn2+ -doped 1D perovskite as excellent down-converting phosphor showcasing the potential application in white light emitting diode. This work not only provides a profound understanding of low-dimensional perovskites but also opens a new way to rationally design high-performance broadband light emitting perovskites for solid-state lighting and displaying devices.

Cerium-based lead-free chalcogenide perovskites for photovoltaics

Inorganic-organic hybrid lead halide perovskites have shown great prospects in solar cells in recent years, and their power conversion efficiency (PCE) has reached up to $25.5%$. However, Pb toxicity and poor ambient stability have remained two unsolved urgent problems. To address these problems, more and more researchers have begun to focus on the application of inorganic lead-free perovskites in the photovoltaic field. Herein, several cerium-based lead-free inorganic chalcogenide perovskites $A{\mathrm{CeTe}}_{3}$ $(A=\mathrm{Ca},\mathrm{Sr},\mathrm{Ba})$ are proposed as suitable optical absorbers for thin-film solar cells based on first-principles calculations. The distorted-phase $A{\mathrm{CeTe}}_{3}$ perovskites are predicted as direct-band-gap semiconductors with a gap value of 1.02--1.13 eV. Moreover, the distorted $A{\mathrm{CeTe}}_{3}$ not only possess a strong optical absorption coefficient $({10}^{5}--{10}^{6}\phantom{\rule{4pt}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1})$, superior to ${\mathrm{MAPbI}}_{3} ({\mathrm{MA}}^{+}={\mathrm{CH}}_{3}{\mathrm{NH}}_{3}^{+})$, but also have excellent PCE, especially for ${\mathrm{BaCeTe}}_{3}$, whose PCE can reach $\ensuremath{\sim}29%$ even in a thin film $(1\ensuremath{\mu}\mathrm{m})$. All these characteristics render distorted $A{\mathrm{CeTe}}_{3}$ perovskites promising photovoltaic materials.

One-dimensional corner-sharing perovskites: Syntheses, structural evolutions and tunable photoluminescence properties

In recent years, organic-inorganic hybrid lead halide perovskites have emerged as a highly promising class of light emitting diodes (LEDs) due to their diverse structures and promising properties. Herein, by choosing various organic molecules as cations, we successfully constructed a series of 1D perovskites of [PMDETA]PbBr5, [PMDETA]PbCl5, [DMPZ][MA]PbBr5, [EEDA][MA]PbCl5, [EPZ][MA]PbCl5 and [EPZ]3Pb2Br10. Under the different structural directing effects of organic cations, these 1D perovskites feature three different kinds of linear or zigzag 1D [PbX5]3− chains based on purely corner-shared octahedrons. As expected, these 1D perovskites exhibit tunable broadband light emissions from blue to yellow spectral range stemming from the self-trapped excitons based on systematical characterizations including time-resolved, temperature-dependent PL emissions and theoretical calculations. This work provides crystal structural engineering for low-dimensional perovskites and paves a new way to regulate the luminescent properties.

Gamma‐Ray Radiation Stability of Mixed‐Cation Lead Mixed‐Halide Perovskite Single Crystals

AbstractOrganic–inorganic hybrid lead halide perovskites have shown extraordinary potentials in space photovoltaic technology and high‐energy‐rays detection but their practical application still faces the bottleneck of radiation‐induced instability. Specifically, gamma‐ray radiation hardness is a main concern due to the highest penetrability and difficulty in stopping of gamma‐photons. However, the gamma‐ray radiation stability of perovskites remains controversial. Herein, stability of mixed‐cation lead mixed‐halide FA0.95Cs0.05PbI2.7Br0.3 single crystals under 60Co gamma‐ray radiation of different doses is investigated by tracking the evolution of structural, optical, and photophysical properties. Importantly, they show excellent stability to humidity and heat, eliminating the potential influence of moisture and temperature upon evaluating their gamma‐ray radiation stability. FA0.95Cs0.05PbI2.7Br0.3 single crystals are found stable with an accumulated dose lower than 200 krad and the performance of the irradiated perovskite photodetector could almost completely self‐heal after aging in dark. Perovskite decomposition occurs when the radiation dose is increased to 400 krad or even higher. These phenomena are explained by the synergistic effect between defects generation and lattice reparation caused by ion redistribution during gamma‐ray radiation. These results provide guidance for their practical application in space photovoltaic technology and gamma‐ray detectors.

Methylammonium Governs Structural and Optical Properties of Hybrid Lead Halide Perovskites through Dynamic Hydrogen Bonding

Methylammonium lead halide perovskites have emerged as ideal materials for photovoltaics and other optoelectronic applications. Their optimal properties stem from complex mechanisms at an atomic level. In these structures, methylammonium molecules undergo continuous temperature-induced reorientations. The underlying atomistic mechanism of this phenomenon and its effect on the material properties are unexplored in many aspects. Here, we address this issue through extensive first-principles and force-field calculations. We show that the interplay between thermal energy and the energetics of molecular orientations fully explains the orthorhombic–tetragonal–cubic phase transitions of the material. The close links among methylammonium orientations, electronic structures, and optical properties are identified. Hydrogen bonding between organic and inorganic sublattices is demonstrated to be the key player in these relationships. We validate our findings against temperature-dependent one-photon and two-photon photoluminescence spectra of CH3NH3PbBr3 and results from the literature. The gained insights can explain the diversity of spectral features observed in the experimental data.

Anharmonic organic cation vibrations in the hybrid lead halide perovskite CH3NH3PbI3

Ultrafast vibrational dynamics of inorganic-organic hybrid lead halide perovskite CH3NH3PbI$ in the room-temperature tetragonal phase is investigated under moderate photoexcitation slightly below the band gap. Time-resolved optical Kerr effect signal exhibits periodic modulations due to the libration and twisting of the methylammonium molecule at 4 and 8 THz, in addition to the inorganic sublattice deformation at 1.2 THz. These oscillations are heavily damped, and their frequencies exhibit blueshifts with increasing pump density, contrary to the expectation from conventional laser heating. Our ab initio lattice dynamics simulations reveal strongly anharmonic vibrational potentials for the zone-center optical phonon modes, and thereby confirm the anharmonicity to be the origin of the experimentally observed frequency blueshifts.

Tuning Dielectric Transitions in Two-Dimensional Organic-Inorganic Hybrid Lead Halide Perovskites.

Organic-inorganic hybrid metal halide perovskites possessing unique two-dimensional (2D)-layered structures have been demonstrated with excellent molecular tunability and stability, especially the promising semiconductor properties for solar cell applications. In this work, three 2D lead halide organic-inorganic hybrid perovskites (IAA)2PbX4 (IAA = isoamylammonium cation and X = Cl, Br, and I) were synthesized by employing a solution processing method and demonstrate distinct tuning solid-state phase transitions coupled with dielectric responses, as well as light absorption properties. Among the title perovskites, the phase transition temperature decreases gradually, and their band gap also indicates a narrowing trend. The results are mainly derived from slight changes in the crystal structure by halogen regulation. These findings might provide an effective crystal engineering strategy for exploring high-performance functional perovskite materials.

1D Chiral Lead Halide Perovskites with Superior Second‐Order Optical Nonlinearity

AbstractChiral hybrid perovskites have shown great potential for applications in next‐generation optoelectronic devices. The intrinsic asymmetric structures of these chiral hybrid perovskites make them particularly promising for second‐order nonlinear optics (NLO). However, it remains still a challenge to obtain ideal perovskite NLO crystals featuring simultaneously large NLO coefficient, good optical transparency, high laser damage threshold, and stable physical and chemical properties, which are highly desirable for practical applications. Herein, a series is constructed of 1D chiral lead halide hybrid perovskites (R/S‐2‐MPD)PbX3 (2‐MPD = 2‐methylpiperidine; X = Cl, Br, I) featuring non‐centrosymmetric architectures. Among them, the (R/S‐2‐MPD)PbBr3 perovskites demonstrate superior performances in second‐order optical nonlinearity, including a large second‐harmonic generation coefficient (≈29.9 pm V–1), wide transparency region (λUV ≈ 310 nm), high laser damage threshold (≈2.84 mJ cm–2), high polarization ratio (up to 96%), and robust physical and chemical stabilities. Such a balanced performance of the chiral lead halide perovskites promises their advanced application in next‐generation photonics devices.

A One-Dimensional Broadband Emissive Hybrid Lead Iodide with Face-Sharing PbI6 Octahedral Chains.

One-dimensional (1D) organic-inorganic hybrid lead halides with unique core-shell quantum wire structures and splendid photoluminescence properties have been considered one of the most promising high-efficiency broadband emitters. However, studies on the broadband emissions in 1D purely face-shared lead iodide hybrids are still rare so far. Herein, we report on a new 1D lead iodide hybrid, (2cepyH)PbI3 (2cepy = 1-(2-chloroethyl)pyrrolidine), characterized with face-sharing PbI6 octahedral chains. Upon UV photoexcitation, this material shows broadband yellow emissions originating from the self-trapped excitons associated with distorted Pb-I lattices on account of the strong exciton-phonon coupling, as proved by variable-temperature emission spectra. Moreover, experimental and calculated results reveal that (2cepyH)PbI3 is an indirect bandgap semiconductor, the band structures of which are governed by inorganic parts. Our work represents the first broadband emitter based on a 1D face-shared lead iodide hybrid and opens a new way to obtain the novel broadband emission materials.

First-principles calculation on electronic properties of Bismuth-halide inorganic perovskites for solar cell

Solar energy is a commonly used alternate source of energy and it can be utilized based on the principle of the photovoltaic effect. The photovoltaic effect converts sun energy into electrical energy using photovoltaic devices (solar cells). A solar cell device should have high efficiency and a long lifetime to be commercially beneficial. Presently, silicon and thin-film solar cells are widely employed. The crystalline solar cells are more efficient but they are also expensive. Thin-film solar cells are formed by placing one or more thin layers of photovoltaic materials on different substrates. Although these cells have a lower cost, they are also less efficient compared to Si-based solar cells. Organic-inorganic hybrid lead halide perovskite solar cells are one of the most promising low-cost power conversion efficiency technologies that could exceed the 26% threshold. However, the lack of environmental stability and of high lead toxicity are the main bottlenecks that impede the future industrialization and commercialization hybrid lead halide perovskite. Hence It is important to achieve high power conversion efficiency while also maintaining stability and non-toxicity in the development of new lead-free perovskite materials.

Local Structure of Multinary Hybrid Lead Halide Perovskites Investigated by Nuclear Quadrupole Resonance Spectroscopy

Hybrid organic–inorganic lead halide perovskites have emerged as popular low-cost, solution-processable semiconductors owing to their outstanding optical and electronic characteristics. The structural characterization of these soft solids has proven challenging due to increased structural dynamics and static disorder. Nuclear quadrupole resonance (NQR) may serve as a powerful tool for probing the local structure of the halide anions in bulk and nanocrystalline forms of these perovskites. Here, we characterize the atomic structure of mixed-cation and mixed-anion solid solutions derived from cubic formamidinium lead iodide (FAPbI3), typically used in photovoltaics and photodetectors, using 127I NQR. Even minute quantities of Cs ions on FA sites or Br ions on I sites lead to a multitude of different local environments, readily seen by NQR spectroscopy. At 10% Cs, signatures of Cs-ion clustering arise, pointing to the onset of the phase separation, observed by diffraction methods at higher Cs contents. On the contrary, Br-ion distribution appears homogeneous across all Br-to-I ratios. We anticipate that halide NQR studies will be indispensable for understanding the atomistic structure of diverse multinary metal halides, also in their diverse forms—from single crystals to thin films and nanocrystals.

Light-Induced Charge Transfer in Two-Dimensional Hybrid Lead Halide Perovskites

Light-Induced Charge Transfer in Two-Dimensional Hybrid Lead Halide Perovskites

New Variants of (110)‐Oriented Layered Lead Bromide Perovskites, Templated by Formamidinium or Pyrazolium

AbstractFour new hybrid lead(II) halide perovskites, γ‐(FA)2PbBr4, (FA)1.5(AA)0.5PbBr4, (PY)(GA)PbBr4 and (PY)(TZ)PbBr4 ((FA)=formamidinium, (AA)=acetamidinium, (PY)=pyrazolium, (GA)=guanidinium and (TZ)=1,2,3‐triazolium), adopt (110)‐oriented layered perovskite structures. While (PY) is found to template the formation of ‘conventional’ (110)‐oriented structure types (i. e. containing staggered [PbBr4]∞ layers), (FA) is shown to facilitate formation of much less common variants based 3 : 1 ordering of the interlayer species or 3×2 step‐like corrugation of the perovskite‐like layers themselves.

Machine Learning Guided Design of Single-Phase Hybrid Lead Halide White Phosphors.

Designing new single‐phase white phosphors for solid‐state lighting is a challenging trial–error process as it requires to navigate in a multidimensional space (composition of the host matrix/dopants, experimental conditions, etc.). Thus, no single‐phase white phosphor has ever been reported to exhibit both a high color rendering index (CRI ‐ degree to which objects appear natural under the white illumination) and a tunable correlated color temperature (CCT). In this article, a novel strategy consisting in iterating syntheses, characterizations, and machine learning (ML) models to design such white phosphors is demonstrated. With the guidance of ML models, a series of luminescent hybrid lead halides with ultra‐high color rendering (above 92) mimicking the light of the sunrise/sunset (CCT = 3200 K), morning/afternoon (CCT = 4200 K), midday (CCT = 5500 K), full sun (CCT = 6500K), as well as an overcast sky (CCT = 7000 K) are precisely designed.

Introducing Intermolecular Cation‐π Interactions for Water‐Stable Low Dimensional Hybrid Lead Halide Perovskites

AbstractOptoelectronically active hybrid lead halide perovskites dissociate in water. To prevent this dissociation, here, we introduce long‐range intermolecular cation‐π interactions between A‐site cations of hybrid perovskites. An aromatic diamine like 4,4′‐trimethylenedipyridine, if protonated, can show a long‐range cation‐π stacking, and therefore, serves as our A‐site cation. Consequently, 4,4′‐trimethylenedipyridinium lead bromide [(4,4′‐TMDP)Pb2Br6], a one‐dimensional hybrid perovskite, remains completely stable after continuous water treatment for six months. Mechanistic insights about the cation‐π interactions are obtained by single‐crystal X‐ray diffraction and nuclear magnetic resonance spectroscopy. The concept of long‐range cation‐π interaction is further extended to another A‐site cation 4,4′‐ethylenedipyridinium ion (4,4′‐EDP), forming water‐stable (4,4′‐EDP)Pb2Br6 perovskite. These water‐stable perovskites are then used to fabricate white light‐emitting diode and for light up‐conversion through tunable third‐harmonic generation. Note that the achieved water stability is the intrinsic stability of perovskite composition, unlike the prior approach of encapsulating the unstable perovskite material (or device) by water‐resistant materials. The introduced cation‐π interactions can be a breakthrough strategy in designing many more compositions of water‐stable low‐dimensional hybrid perovskites.

Tuning Facets and Controlling Monodispersity in Organic–Inorganic Hybrid Perovskite FAPbBr3 Nanocrystals

Lead halide hybrid perovskite nanocrystals are considered as one of the most efficient light-harvesting materials in current research. However, unlike all-inorganic perovskite nanocrystals, the quality optimization and synthetic progress for facet tuning of these hybrid nanocrystals have not moved forward at the same pace. To meet the current demand for high-quality, facet-tuned, and monodisperse nanocrystals, herein, surface A-site cations’ population-controlled facet tuning of FAPbBr3 nanocrystals is reported. Using specific alkylammonium ligands obtained from α-bromo ketones and comparing their concentration with FA+, cubic, dodecahedral, and quasi-spherical shapes of nanocrystals in cubic phase are obtained having monodispersity comparable to that of their best reports. In addition, upon changing of surface ligands, spontaneous formation of self-assembled blue-emitting platelets was also observed. Because of the importance of these materials, these findings will aid the fundamental understanding of formation of hybrid perovskite nanocrystals and also support accelerating their widespread applications.

A Photoluminescent Lead Bromide Hybrid Perovskite Molecular Ferroelastic Semiconductor with Sequential High-Tc Phase Transitions.

Organic-inorganic hybrid lead halide perovskites have attracted great interest for their use in promising optoelectronic applications. However, reports of photoluminescent perovskite molecular ferroelastic semiconductors with sequential high-Tc phase transitions have been scarce. In this work, a one-dimensional lead bromide hybrid perovskite [N,N-dimethylethanolammonium]PbBr3 has been synthesized, undergoing high-Tc sequential phase transitions at around 351 and 444 K, higher than those of most previously discovered hybrid perovskite phase transition materials. The specific intermolecular hydrogen bond between cationic molecules provides the greatest contribution to its high Tc by increasing the barrier of molecular motion under the temperature stimuli. The prominent ferroelastic domain evolution is visually observed under orthogonally polarized light. In addition, [N,N-dimethylethanolammonium]PbBr3 exhibits semiconducting and orange light emission characteristics. This finding opens up an avenue for designing high-performance ferroelastic materials and provides great motivation for discovering new multifunctional materials for the next generation of smart devices.

Spatiodynamics, Photodynamics, and Their Correlation in Hybrid Perovskites

The motion of organic cations and its possible correlation with excited state photodynamics are important to the fundamental understanding of the superior performances of 2D and 3D hybrid lead-halide perovskites (LHPs) in optoelectronic applications. Herein, variable-temperature (VT) solid-state 1H and 13C CP (Cross Polarization) NMR spectroscopy without isotope enrichments, combined with VT powder XRD, differential scanning calorimetry (DSC) and time-resolved photoluminescence (TRPL), was employed to study the phase transition, local structure, motion dynamics and photodynamic behaviors of organic cations in hybrid 2D Ruddlesden-Popper perovskites (BA)2(MA)n-1PbnI3n+1 (BA denotes butylammonium and MA denotes methylammonium). Two types of BA conformations in various crystalline phases of 2D RPPs and conformational transition associated with phase transition were clearly revealed. Quantitative NMR analyses suggest that the rotation dynamics of MA in 2D RPPs is comparable to that of MA in 3D MAPbI3. A surprising linear relationship was discovered between the estimated activation energy of the MA rotation and logarithm of photoluminescence (PL) lifetimes (τ) of 2D RPPs and MAPbI3, strongly supporting the presence of coupling between the cation spatial dynamics and the excited state photodynamic behavious.

Mobile Media Promotes Orientation of 2D/3D Hybrid Lead Halide Perovskite for Efficient Solar Cells.

2D/3D hybrid perovskites have shown great environmental stability for use as solar cells. Yet insulating organic cation spacers affect the formation of vertically oriented crystalline grains to hamper carrier transport. To date, the selection of cation spacers is limited because crystal growth kinetics should be strictly obeyed. Here, we adopted a mobile-media-assisted method to fabricate highly oriented 2D/3D hybrid perovskite films, wherein bulky molecules of (C(CH3)3NH3, TBA) are used as cation spacers. We found the compositional volatile salt promote the orientation of perovskite polycrystalline films with various compositions universally. And we obtained efficient solar cells with a photoelectric conversion efficiency (PCE) of 17.38% and a certified PCE of 19.30% based on 2D/3D hybrid perovskites an overall stoichiometry matching n = 10 and 20, respectively, which are one of the highest efficiencies among all 2D/3D hybrid perovskite based solar cells so far. These findings largely broaden the selection category of bulky cations and promote further exploration of more functional organic cations.

Interface engineering for high-efficiency perovskite solar cells

The power conversion efficiency of thin film solar cells using organic–inorganic hybrid lead halide perovskite as an absorber has achieved over 25%. An augment of the output voltage can further increase the efficiency approaching the Shockley–Queisser efficiency limitation, which is highly correlated with charge carrier management at interfaces in perovskite devices. This perspective presents some considerations to improve carrier transfer and reduce recombination loss for highly efficient perovskite solar cells, including primary requests on charge carrier transfer dynamics, reasonable design methodologies of interfacial materials, and tuning interface interaction between perovskite and charge transport layers.