Metal Halide Perovskites Research Articles

Structural Stability of Mixed‐Halide Perovskite Nanocrystals in Energy Storage: The Role of Iodine Expulsion

AbstractIn the pursuit of efficient optoelectronics devices, hybrid lead halide perovskite quantum dots (PQDs) have emerged as highly promising semiconductor materials due to their intriguing properties. While these materials have been used in many applications, the fundamental understanding of their behavior remains relatively unexplored, especially for the mixed halide perovskite samples. To facilitate the advancement of PQD technologies for commercial applications, it is essential to gain insights into the role of ion migration. This study delves into the fundamental aspects of ion migration in halide perovskite nanocrystals. Porous electrodes for supercapacitor application were fabricated using CsPbBr3–xIx (x=0,1,2) nanocrystals prepared via the ligand‐assisted re‐precipitation (LARP) method. Three‐electrode electrochemical measurements and several other characterizations were conducted under dark conditions to evaluate device performance and elucidate the impact of mixed halides on device kinetics and stability. X‐ray photoelectron spectroscopy before and after the electrochemical measurement reveals intriguing findings. Notably, the analysis uncovered the phase segregation in the metal halide perovskite nanocrystals with particular emphasis on CsPbBr2I due to its distinctive mixed‐halide behavior. The specific capacitance increases with the increasing cycles. Interestingly, as the iodide content increases, there is no selective halide expulsion as the structure collapses rapidly.

Highly stable and self-powered ultraviolet photodetector based on Dion-Jacobson phase lead-free double perovskite

Metal halide perovskite materials present a wide array of opportunities for the development of high-performance optoelectronic devices, owing to their outstanding photoelectric properties. Compared with the lead-containing perovskites, stable and non-toxic organic-inorganic hybrid perovskites exhibit enhanced potential for future commercial applications. In this work, we developed a self-powered UV photodetector based on 2D Dion−Jacobson (DJ) phase lead-free double perovskite HAAg0.5Bi0.5Br4 (HA2+ = histammonium) perovskite with an on-off ratio up to 2.66 × 106, excellent specific detectivity of 6 × 1012 Jones, and response speed of 1.32 ms/118.4 μs. The light intensity related pyro-phototronic effect on 2D perovskite is thoroughly investigated. Temperature and light detection are realized through multi-energy coupling, which greatly improves the detection performance. Coupled pyro-phototronic current is calculated nearly 75 folds higher than that from the photoelectronic merely. As-prepared photodetector film shows excellent stability in normal environment, maintaining a value of 90 % to the initial performance after 500 cycles and 90 days. This work provides a new self-powered, stable and non-toxic candidate for the future UV photodetectors.

Ions-induced Assembly of Perovskite Nanocomposites for Highly Efficient Light-Emitting Diodes with EQE Exceeding 30.

Metal halide perovskites, a cost-effective class of semiconductos, hold great promise for display technologies that demand high-efficiency, color-pure light-emitting diodes (LEDs). Early research on three-dimensional (3D) perovskites showed low radiative efficiencies due to modest exciton binding energies. To inprove luminescence, reducing dimensionality or grain size has been a common approach. However, dividing the perovskite lattice into smaller units may hinder carrier transport, compromising electrical performance. Moreover, the increased surface area introduce additional surface trap states, leading to greater non-radiative recombination. Here, an ions-induced growth method is employed to assembe lattice-anchored perovskite nanocomposites for efficient LEDs with high color purity. This approach enables the nanocomposite thin films, composed of 3D CsPbBr3 and its variant of zero-dimensional (0D) Cs4PbBr6, to feature significant low trap-assisted nonradiative recombination, enhanced light out-coupling with a corrugated surface, and well-balanced charge carrier transport. Based on the resultant 3D/0D perovskite nanocomposites, the perovskite LEDs (PeLEDs) achieving an remarkable external quantum efficiency of 31.0% at the emission peak of 521 nm with a narrow full width at half-maximum of only 18 nm. This sets a new benchmark for color purity in high performance PeLED research, highlighting the significant advantage of this approach.

Unlocking Enhanced Light Harvesting in Perovskites: A Light‐Mediated Ligand Management Approach

AbstractInterfaces between nanocrystals and their stabilizing ligands in light‐harvesting devices are crucial for mediating energy transfer, essential for efficient solar energy conversion. In metal halide perovskites, a promising material for these devices, Förster resonance energy transfer (FRET) within perovskite/acceptor‐molecule complexes offers a pathway for optimized energy transfer. However, traditional methods for optimizing FRET in perovskite‐chromophore hybrids are based on static modifications. This study presents an innovative approach for light‐driven dynamic control of FRET, achieving an ≈14% enhancement in efficiency between CsPbBr3 nanocrystals (CPB NCs) and rhodamine B isothiocyanate (RITC) dye. UV light is utilized to reversibly regulate NC‐ligand binding and thus control the coupling between CPB NCs and RITC at their interface. This approach critically relies on strong NC–ligand interactions, such as the Pb─S bond between CPB NCs and RITC. Light exposure weakens the binding of surface ligands, allowing RITC, with its strong bond, to attach more effectively and promote enhanced energy transfer. This light‐activated control is absent with Rhodamine B (RhB) lacking ─NCS group, a strong binding motif. The findings reveal the importance of NC–ligand interactions in dynamically manipulating FRET with light. This pioneering method for nanoscale FRET control paves the way for more efficient light‐harvesting devices.

Multicolor and multimode luminescent lanthanide-doped Cs2NaInCl6:Sb3+ from visible to near infrared for versatile applications

Double halide perovskites have shown admirable potential in promising optoelectronic applications due to simple synthesis, good stability and high structural tolerance. However, the poor optical properties caused by the parity-forbidden transitions posts a stringent limitation on their potential applications. Herein, we dope the lanthanide (Ln3+) ions with abundant energy levels into the Cs2NaInCl6:Sb3+ single crystals, which not only achieve multicolor visible emissions spectra from blue to red light, but also expand to the near infrared region from 800 to 1900 nm. In addition, the phosphors enable the multimode emissions with the up-conversion and down-conversion photoluminescence. Intriguingly, the excitation source, and the excitation light intensity also endow the multicolor emissions. Thus, combining with the multicolor and multimode luminescent properties, Cs2NaInCl6:Sb3+/Ln3+ could be applied to night vision imaging, substance detection, optical thermometry, white-light-emitting diodes (WLEDs) and anti-counterfeiting. The maximum value of relative temperature sensitivity reaches as high as 1.207 % K−1, which is relatively higher than those of most metal halide perovskites. Moreover, the single-source WLED displays Commission Internationale de L'Eclairage color coordinates (0.32, 0.31), a correlated color temperature of 6673 K, and color rendering index of 81.7. These results demonstrate the potential applications in the multifunctional photoelectric applications.

Indirect to direct band gap transition of ABI3 (A = Rb, Cs; B = Ca, Sr) perovskites under hydrostatic pressure for photovoltaic and optoelectronic applications: A DFT study

The objective of this study is to enhance the utilization of ABI3 (A = Rb, Cs; B = Ca, Sr) metal-halide perovskites in multiple forms of technological applications by investigating their structural, electronic, optical, and mechanical characteristics using the ab initio method. At ambient pressure, the geometry-optimized lattice constants for RbCaI3, RbSrI3, CsCaI3, and CsSrI3 are 6.19 Å, 6.45 Å, 6.22 Å, and 6.47 Å, respectively, consistent with prior research. Additionally, a significant decrease in lattice parameters and bond length is observed, which leads to increased levels of atomic interactions. Pressure narrows the band gap from the ultraviolet-to-visible region. This phenomenon promotes the transfer of electrons from the valence-to-conduction band, hence improving the performance of optoelectronic devices. Furthermore, a shift from an indirect to a direct band gap is induced by the application of pressure, which improves the material's suitability for photovoltaic applications. The covalent and ionic nature of Ca/Sr-I and Rb/Cs-I under pressure and without pressure conditions was determined using the charge density maps. Enhanced pressure significantly boosts optical absorption and conductivity in the visible spectrum, implying substantial potential for improving the efficacy of perovskite solar cells and photonic devices. Additionally, applied pressure significantly influences the mechanical properties of the entitled perovskites, leading to higher ductility and anisotropy. As a whole, this study offers insights into the scientific applications of non-toxic perovskites in different pressure environments.

Semi-Opaque Perovskite Solar Cells.

Transparent photovoltaics are garnering significant interest for power generation in applications where light transmission is required. Metal halide perovskites have emerged as one of the most lucrative material classes for such device architectures due to their exceptional optoelectronic properties, and compositional versatility enabling a wide range of transparency levels. While research has primarily focused on semitransparent solar cell architectures, their colored appearance, and efficiency limitations hinder their practical applicability. In this perspective, we look at semiopaque perovskite solar cells as an alternative technological approach that comprises partially covered surfaces to enable light transmission. Our comparative analysis reveals that such semiopaque devices have the potential for superior efficiencies while maintaining a color-neutral appearance. These benefits are met with a number of hurdles, which provide key areas for future innovation to see the realization of such devices in real world applications.

Ion Leakage Current Control for Polycrystalline Metal Halide Perovskite Direct X-ray Detectors.

Metal halide perovskites have emerged as promising materials for X-ray detection due to their high X-ray attenuation coefficients, defect tolerance, and suitability for large-area, low-temperature fabrication. However, the intrinsic high ion conductivity of these materials presents challenges, such as high dark current density and current drift, which impair the stability and sensitivity of perovskite X-ray detectors. This study introduces an approach to mitigating these issues by incorporating 2,2,3,3,3-pentafluoropropylamine hydrochloride (PFH) into polycrystalline MAPbI3-xClx films using a one-step blade-coating method. PFH aggregates at grain boundaries, raising local vacuum energy levels and passivating surface defects, thereby reducing ion conductivity without affecting electron conductivity. As a result, this approach significantly reduces the dark current and enhances sensitivity, achieving a low detection limit of 14.7 nGyair/s. Additionally, it improves signal stability, consistency, and response speed of the detector. These findings suggest that PFH is a promising additive for advancing the performance and practical application of polycrystalline metal halide perovskite-based X-ray detectors.

Reduced-Dimensional Perovskites: Quantum Well Thickness Distribution and Optoelectronic Properties.

Reduced-dimensional perovskites (RDPs), a large category of metal halide perovskites, have attracted considerable attention and shown high potential in the fields of solid-state displays and lighting. RDPs feature a quantum-well-based structure and energy funneling effects. The multiple quantum well (QW) structure endows RDPs with superior energy transfer and high luminescence efficiency. The effect of QW confinement directly depends on the number of inorganic octahedral layers (QW thickness, i.e., n value), so the distribution of n values determines the optoelectronic properties of RDPs. Here, it is focused on the QW thickness distribution of RDPs, detailing its effect on the structural characteristics, carrier recombination dynamics, optoelectronic properties, and applications in light-emitting diodes. The reported distribution control strategies is also summarized and discuss the current challenges and future trends of RDPs. This review aims to provide deep insight into RDPs, with the hope of advancing their further development and applications.

Interface Energy-Level Reorganization for Efficient Perovskite γ-Ray Detectors.

Metal halide perovskites are promising candidates for γ-rayspectrum detectors. However, achieving high-resolution energy spectra in single-photon pulse-height analysis mode remains challenging, due to the inevitable leakage currents degrade the recognizable fingerprint energies which is critical for resolving γ-ray spectroscopy. We demonstrate under high bias voltage, a deficient contact barrier can lead to excessive surface charge injection, thereby increasing leakage current from electrodes to perovskites. Hence, we conceive to employ surface ligand engineering on perovskite single crystals to manipulate energy levels to suppress leakage current. In particular, anchoring a strong dipole ligand onto the perovskite induced surface charge-density displacement, leading to a downward band bending and heightened the corresponding contact barrier. Consequently, the strategy minimized the detectors'leakage current by an order of magnitude, to as low as 44 nA cm-2. The resulting detectors show a significant improvement in energy resolution, 3.9% for 22Na 511 keV γ-rays has been achieved at room temperature. The resulting detector further resolves each fingerprint energy for 152Eu γ-spectrum, representing one of the best γ-rays perovskite detectors reported to date. Moreover, the detectors exhibited stabilized energy resolution without any degradation under a continuous electric fieldfor over 300 minutes, representing the longest longevity reported to date.

Hydroxyl-driven construction of dual-emitting CsPbBr3/EuWO4(OH) composite for radiometric thermometer and information encryption applications

Self-assembled inorganic metal halide perovskite composites with high emitting efficiency, tunable multimode emission and stimuli-responsive luminescence demonstrated great potential in diversified luminescence applications. Here, a novel CsPbBr3/EuWO4(OH) composite was successfully prepared through the surface adsorption of Pb2+ ions on hydroxylated EuWO4(OH) microsheets and subsequent nucleation of CsPbBr3 peroviskite quantum dots (PQDs) by the anti-solvent crystallization in CsBr containing N,N-dimethylformamide (DMF) solution. Due to the distinct fluorescent thermochromic switching properties of temperature-insensitive Eu3+ and sensitive CsPbBr3 PQDs emitting centers, the resultant CsPbBr3/EuWO4(OH) composite exhibits excellent ratiometric temperature sensing performance. The CsPbBr3/EuWO4(OH) thermometer based on the fluorescence intensity ratio (FIR) technique originating from emissions of Eu3+ to CsPbBr3 PQDs was then explored with a high temperature sensitivity (Sr) of 5.8 % ℃−1 at 54 ℃. In addition, a high-security-level information encryption scheme was proposed by utilizing the excitation-wavelength-dependent switchable fluorescence of CsPbBr3/EuWO4(OH) composite. This study provides a simple and feasible strategy for assembling dual-emission CsPbBr3/EuWO4(OH) composite, showing potential applications in optical ratiometric thermometry and information encryption fields.

Tb3+-doped a zero-dimensional all-inorganic metal halide perovskite scintillator Cs2ScCl5·H2O for X-ray imaging

All-inorganic zero-dimensional (0D) metal halide perovskite materials have been widely studied in solid-state lighting due to their unique optical properties. However, there are few researchs on their potential applications in X-ray imaging. Herein, we synthesized an all-inorganic 0D metal halide perovskite scintillator, Cs2ScCl5·H2O:Tb3+, was prepared by using a hydrothermal method. Upon 240 nm excitation, the emission spectrum of Cs2ScCl5·H2O:Tb3+ is primarily composed of characteristic emissions from Tb3+, with the strongest emission peak at 548 nm. Additionally, under X-ray excitation, it exhibits blue light showing an intense emission band centered at 425 nm due to self-trapped (STE) emission, and a rather weaker green emission caused by energy transfer from STE emission to Tb3+ ions. Based on this, a flexible film prepared by using the as-obtained scintillator Cs2ScCl5·H2O:Tb3+ demonstrates real-time X-ray imaging with a resolution of 9.5 lp mm−1. These results suggest the potential application prospect of Cs2ScCl5·H2O:Tb3+ in X-ray detection and imaging.

Revealing and Inhibiting the Facet-related Ion Migration for Efficient and Stable Perovskite Solar Cells.

Ion migration is a major issue hindering the long-term stability of perovskite solar cells (PSCs). As an intrinsic characteristic of metal halide perovskite materials, ion migration is closely related to the atomic arrangement and coordination, which are the basic characteristic differences among various facets. Herein, we report the facet-related ion migration, and then achieve the inhibition of ion migration in perovskite through finely modulating the facet orientation. We show that the (100) facet is substantially more vulnerable to cationic migration than the (111) facet. The main reason for this difference in migration is that the cationic migration route in the (111) facet deviates from that in the (100) facet, which increases the active migration energy and weakens the contribution from the electric field during operation. We prepare a (111)-dominated perovskite film by incorporating a facile and green addition of water (H2O) into the antisolvent, further achieving a power conversion efficiency (PCE) of 26.0 % (25.4 % certification) on regular planar PSCs and 25.8 % on inverted PSCs. Moreover, the unencapsulated PSCs can maintain 95 % of their initial PCE after 3500-hours operation under simulated AM1.5 illumination at the maximum power point.

Unleashing the Potential: High Responsivity at Room Temperature of Halide Perovskite-Based Short-Wave Infrared Detectors with Ultrabroad Bandwidth.

Short-wave infrared (SWIR) imaging systems offer remarkable advantages, such as enhanced resolution and contrast, compared to their optical counterparts. However, broader applications demand improvements in performance, notably the elimination of cryogenic temperature requirements and cost reduction in manufacturing processes. In this manuscript, we present a new development in SWIR photodetection, exploiting the potential of metal halide perovskite materials. Our work introduces a cost-effective and easily fabricated SWIR photodetector with an ultrabroad detection range from 900 to 2500 nm, a room-temperature responsivity of 1.57 × 102 A/W, and a specific detectivity of 4.18 × 1010 Jones at 1310 nm. We then performed comprehensive static and time-resolved optical and electrical measurements under ambient conditions, complemented by extensive density functional theory simulations, validating the formation of heterojunctions within the intrinsic n-type and extrinsic p-type perovskite structures. The potential of our perovskite-based SWIR materials extends from photodetectors to photovoltaic cells and introduces a possibility for high SWIR responsivity at room temperature and atmospheric pressure, which promotes its economic efficiency.

Revealing and Inhibiting the Facet‐related Ion Migration for Efficient and Stable Perovskite Solar Cells

Ion migration is a major issue hindering the long‐term stability of perovskite solar cells (PSCs). As an intrinsic characteristic of metal halide perovskite materials, ion migration is closely related to the atomic arrangement and coordination, which are the basic characteristic differences among various facets. Herein, we report the facet‐related ion migration, and then achieve the inhibition of ion migration in perovskite through finely modulating the facet orientation. We show that the (100) facet is substantially more vulnerable to cationic migration than the (111) facet. The main reason for this difference in migration is that the cationic migration route in the (111) facet deviates from that in the (100) facet, which increases the active migration energy and weakens the contribution from the electric field during operation. We prepare a (111)‐dominated perovskite film by incorporating a facile and green addition of water (H2O) into the antisolvent, further achieving a power conversion efficiency (PCE) of 26.0% (25.4% certification) on regular planar PSCs and 25.8% on inverted PSCs. Moreover, the unencapsulated PSCs can maintain 95% of their initial PCE after 3500‐hours operation under simulated AM1.5 illumination at the maximum power point.

Application of Metal Halide Perovskite in Internet of Things.

The Internet of Things (IoT) technology connects the real and network worlds by integrating sensors and internet technology, which has greatly changed people's lifestyles, showing its broad application prospects. However, traditional materials for the sensors and power components used in the IoT limit its development for high-precision detection, long-term endurance, and multi-scenario applications. Metal halide perovskite, with unique advantages such as excellent photoelectric properties, an adjustable bandgap, flexibility, and a mild process, exhibits enormous potential to meet the requirements for IoT development. This paper provides a comprehensive review of metal halide perovskite's application in sensors and energy supply modules within IoT systems. Advances in perovskite-based sensors, such as for gas, humidity, photoelectric, and optical sensors, are discussed. The application of indoor photovoltaics based on perovskite in IoT systems is also discussed. Lastly, the application prospects and challenges of perovskite-based devices in the IoT are summarized.

Brightening dark excitons in inorganic halide perovskites by local symmetry breaking

Thermally activated delayed fluorescence (TADF) phenomenon, defined as thermal activation of triplet dark-state excitons into singlet state excitons through reverse intersystem crossing (RISC), has become a prevalent principle for designing organic-based electro-/photo-luminescent molecules. However, activating dark excitons in inorganic metal halide perovskites (MHPs) still remains challenging. Herein, we report an efficient strategy of doping-induced local symmetry breaking to brighten dark excitons in inorganic halide perovskite Cs2ZrCl6, which result in a 500 % enhancement of low-temperature luminescence emission. Lattice symmetry breaking confirmed by the X-ray absorption spectroscopy measurements could disturb the local coordination environment at the Zr site. The singlet-triplet energy gap (ΔEST) fitted from temperature-dependent photoluminescence decay curves decreases from 0.087 to 0.071 eV, thus reducing up-conversion barrier of dark excitons. Theoretical calculation indicates large spatial separation of charge density favorable for enhanced TADF emission. Furthermore, a flexible X-ray scintillator screen with poly (dimethylsiloxane) as the matrix could obtain high-quality X-ray imaging with a 14 lp mm−1 resolution. This work gives insights into improving photoemission of inorganic MHPs via brightening dark excitons.

Growth and characterization of highly efficient Cs[formula omitted]Cu[formula omitted]I[formula omitted] single crystal for [formula omitted]-ray detection

Metal halide perovskites, particularly zero-dimensional (0D) variants, have garnered significant attention as scintillator materials for various applications such as γ-ray spectroscopy, X-ray imaging, and security. Among these, Cs3Cu2I5 has emerged as a promising candidate owing to its exceptional characteristics, such as good energy resolution, high light output, and high stopping power. Although there is sufficient data available on the scintillation properties of Cs3Cu2I5 Single Crystal (SC) grown using various methods, there still remains a scarcity of data on the scintillation properties of SCs grown using solvent evaporation method at room temperature. In the present work, Cs3Cu2I5 SCs have been grown using the solvent evaporation method at room temperature and characterised for their structural, optical, and scintillation properties. The SC shows an orthorhombic structure with a bandgap of 3.58 eV. The optical properties of the SC reveal the existence of Self-Trapped Exciton (STE). The SC exhibits an energy resolution of 5.80 ±0.05% at 662 keV and a light output of 41,000 photons/MeV, making it suitable for γ-rays detection. The intrinsic photopeak efficiencies of Cs3Cu2I5 SC for γ-rays are reported for the first time. GEANT4 simulation toolkit has been used to perform realistic simulations, and the simulated and experimental efficiencies are compared. Simulations show that Cs3Cu2I5 scintillator has twice the efficiency of the NaI:Tl scintillator.

Metal Halide Perovskites for Photocatalysis: Performance and Mechanistic Studies.

Metal halide perovskites, both lead-based and lead-free variants, have emerged as highly versatile materials with widespread applications across various fields, including photovoltaics, optoelectronics, and photocatalysis. This review provides a succinct overview of the recent advancements in the utilization of lead and lead-free halide perovskites specifically in photocatalysis. We explore the diverse range of photocatalytic reactions enabled by metal halide perovskites, including organic transformations, carbon dioxide reduction, and pollutant degradation. We highlight key developments, mechanistic insights, and challenges in the field, offering our perspectives on the future research directions and potential applications. By summarizing recent findings from the literature, this review aims to provide a timely resource for researchers interested in harnessing the full potential of metal halide perovskites for sustainable and efficient photocatalytic processes.

Impact of carbon electrode layer on the series resistance and fill factor of CH3NH3PbI3 perovskite solar cell

Methylammonium lead triiodide (CH3NH3PbI3) is a metal halide perovskite that is attracting great attention owing to its remarkable optoelectronic properties especially in perovskite solar cells (PSCs) and perovskite light-emitting devices (PLEDs). In this work, the impact of the number of carbon electrode layers on the photovoltaic parameters and impedance spectra of hole transport material-free (HTM-free) glass/FTO/c-TiO2/m-TiO2/m-ZrO2/carbon monolithic PSCs is examined. A significant influence of the carbon electrode layers on the fill factor and series resistance is revealed. The optimum values of fill factor and series resistance are observed when a 3-layered carbon electron is used in the PSC. This is due to higher charge transportation, higher electrical conductivity, higher electron mobility, and lower recombination losses.