Organic-inorganic Lead Halide Perovskite Materials Research Articles

(Invited) Amplified Spontaneous Emission Dynamics of a Lead Halide Perovskite Crystal as Revealed by Femtosecond Transient Absorption Microscopy

Organic-inorganic lead halide perovskite materials (e.g. CH3NH3PbX3, CsPbX3, X=Cl, Br, I) have various attractive properties not only for solar cells but also for LED and nanoscale lasers because of their wavelength tunability and low lasing threshold. Such an efficient lasing is indispensable for their applications, and the essential needs are miniaturization and low threshold. While this material was reported in 2009 for use in solar cells, it is also expected to be used in light-emitting and laser devices due to its easy tunability of emission wavelength and low-cost fabrication. However, the low-threshold lasing mechanism of lead halide perovskites has not been established due to various theories on the interaction state between light and carriers generated in the cavity at the initial stage and the carrier-carrier interaction state, which has greatly hindered progress in improving performance. In the present study, we have measured transient absorption spectra of a single CH₃NH₃PbBr₃ microcrystal using a femtosecond transient absorption microscopy to reveal the initial carrier process that induces nonlinear luminescence[1].CH3NH3PbBr3 crystals were prepared by a previously reported method. Aqueous lead(II) acetate solution (100 mg/mL) was dropped onto a glass slide and dried at 60°C for 30 min to obtain a film of lead acetate. Microcrystals of CH3NH3PbBr3 were then obtained by immersing the film in methylammonium bromide solution (5 mg/mL) with isopropanol as a solvent for 20 hours at room temperature in air.For transient absorption measurements, a regeneratively amplified femtosecond pulse (Spectra-Physics, Solstice, 795 nm, 1 kHz) was split in two; the second harmonic of one beam was used as the excitation light, and the white light generated with the other beam by introducing it into an optical parametric amplifier (Light Conversion, TOPAS) and focusing the obtained signal light (1.3 mm) into a CaF2 plate was used as the probe light.Fig. 1(a) shows the transient absorption spectra of lead halide perovskite excited at the intensities over the lasing threshold. The spectral signals that were not observed before the time origin (-1 ps) were significantly observed with modulated spectral shape after the time origin (≥0 fs). The spectral bleaching around 540 nm indicates carrier generation by the excitation light, and the relaxation of the bleaching indicates the recombination of electrons and holes. Furthermore, at around 557 nm, a bleaching signal appeared as shown in Fig. 1(b), that was not represented in the transient absorption spectrum excited at the intensity below the lasing threshold. This signal is suggested to be due to amplified stimulated emission. Spectral modulation is often observed as interference of light propagating in thin-film systems. The thickness of the perovskite crystals is around 200-300 nm, which is suitable to observe the optical interference. However, generally, this interference tends to become lower in frequency as one observes longer wavelengths, which is essentially different from the modulation observed here. The spectra modulation appeared immediately after the carrier was generated, and the modulation continued for up to 1ns. These results suggest that the modulation is caused by the electric field effect of the generated carriers on the electron spectrum. Franz-Keldysh’s theory is often used for spectral modulation in the presence of an electric field. In reflectance transient absorption spectroscopy, the electric field modulated spectrum has been explained in the GaInP2 system by Franz-Keldysh’s theory in systems where charges are generated on the semiconductor surfaces[2]. These results indicate the spectral modulation occurred from the charges separated on the surface of the crystal. We will discuss the mechanism of amplified spontaneous emission and low threshold lasing dynamics at the conference site. Funding: This study was partly supported by KAKENHI (Grant Number JP22H04755, JP19K05190) and JST FOREST (JPMJFR213G).

Fusing Science with Industry: Perovskite Photovoltaics Moving Rapidly into Industrialization.

The organic-inorganic lead halide per materials have emerged as highly promising contenders in the field of photovoltaic technology, offering exceptional efficiency and cost-effectiveness. The commercialization of perovskite photovoltaics hinges on successfully transitioning from lab-scale perovskite solar cells to large-scale perovskite solar modules (PSMs). However, the efficiency of PSMs significantly diminishes with increasing device area, impeding commercial viability. Central to achieving high-efficiency PSMs is fabricating uniform functional films and optimizing interfaces to minimize energy loss. This review sheds light on the path toward large-scale PSMs, emphasizing the pivotal role of integrating cutting-edge scientific research with industrial technology. By exploring scalable deposition techniques and optimization strategies, the advancements and challenges in fabricating large-area perovskite films are revealed. Subsequently, the architecture and contact materials of PSMs are delved while addressing pertinent interface issues. Crucially, efficiency loss during scale-up and stability risks encountered by PSMs is analyzed. Furthermore, the advancements in industrial efforts toward perovskite commercialization are highlighted, emphasizing the perspective of PSMs in revolutionizing renewable energy. By highlighting the scientific and technical challenges in developing PSMs, the importance of combining science and industry to drive their industrialization and pave the way for future advancements is stressed.

Short review on self-healing perovskite Materials: Advances and prospects

One primary area of research the world over is regarding the consumption of energy without causing harm to our environment. In this paper, a review of current advancements in the sphere of combining photovoltaic devices with self-healing technology is presented. The durability of solar cells is a crucial aspect for long-term usage. The two different categories of systems investigated herewith are polycrystalline self-healing perovskites and lead-free self-healing perovskites. There have been in-depth discussions on current trends in the selection of organic–inorganic lead halide perovskite materials for perovskite solar cells, as well as significant elements that affect the operations of solar cells. This article provides a thorough overview of current developments in the field of self-healing perovskites and presents a roadmap for creating lead-free self-healing perovskites that are more durable, stable, and effective.

Observation of electronic spectra modulation in a CH3NH3PbBr3 crystal by utilizing transient absorption microscopy

Organic–inorganic lead halide perovskite materials have attractive properties not only for solar cells but also for LED because of their high performance and wavelength tunability. Such an efficient light-emitting and lasing nature are indispensable for their applications, and the essential needs are miniaturization and low lasing threshold. One material that satisfies these requirements is lead halide perovskite. To understand the time evolution of the interaction between light and matter in a perovskite crystal system, it is necessary to reveal the carrier dynamics in each crystal. In this study, the transient absorption spectra of CH3NH3PbBr3 crystals were measured using a femtosecond transient absorption microscopy. Surprisingly, strong spectra modulation has been observed and these results indicate the charge separation on the surface of the crystal. Amplified spontaneous emission dynamics were also observed in the transient absorption spectra.

Are Halide‐Perovskites Suitable Materials for Battery and Solar‐Battery Applications–Fundamental Reconsiderations on Solubility, Lithium Intercalation, and Photo‐Corrosion

AbstractIn recent years the development of autonomous photo‐rechargeable batteries has received growing attention. Especially highly integrated photobatteries based on multifunctional materials able to harvest sunlight and store charge carriers are the holy grail amongst such devices. Recently 2‐(1‐cyclohexenyl)ethyl ammonium lead iodide (CHPI) has been reported as multifunctional photoelectrode material for the design of highly integrated Li‐ion photobatteries. CHPI is thereby believed to be able to reversibly intercalate Li‐ions from polar carbonate‐based electrolytes, typically used in Li‐ion batteries (LIBs). Herein, CHPI is examined closer to investigate its stability against dissolution, the possibility of Li‐intercalation and photo‐assisted deintercalation, and its general behavior under illumination in standard carbonate‐based electrolytes as well as in a newly developed low polarity electrolyte based on ortho‐difluorobenzene (o‐DFB). This study demonstrates that CHPI dissolves in contact with carbonate‐based electrolytes while being stable in o‐DFB‐based electrolyte and that no Li‐intercalation takes place in the latter. Furthermore, CHPI irreversibly photo‐corrodes during illumination and photo‐assisted deintercalation of lithium ions is not detected. These results lead to the conclusion, that CHPI is neither a suitable nor a stable material for the design of Li‐ion‐based photo‐rechargeable batteries and similar behavior for other organic–inorganic lead halide perovskite materials is expected.

Construction of nanostructured CH3NH3PbI3 layer for high-performance perovskite solar cells by Ar plasma etching

Organic-inorganic lead halide perovskite materials have attracted wide attention owing to their great optoelectronic properties and low-temperature solution processability. Mesostructured perovskite solar cells (PSCs) could help to further improve the photovoltaic property. However, the existing approaches by inserting a layer of metal-oxide are generally need special treatment and consume much energy. In this work, an Ar plasma etching method is employed to modify composition of the perovskite absorb material with its morphology remain unchanged, which can effectively avoid unfavorable defects and enhance the charge separation efficiency. Based on controllable pore structure and porosity, the idiosyncratic mesostructured perovskite solar cells yield an 18.7% improvement in power conversion efficiency as compared with the common planar-type counterparts. Therefore, this method offers a room temperature scheme for high-performance mesostructured perovskite solar cells, making the flexible PSC possible.

Reversible photochromic and photoluminescence in iodide perovskites

Color imaging experiment demonstrates a photochromic behavior of mixed-halide perovskites upon dark and light excitation, while the color emitted by the crystals changes from red to yellow and vice versa with the intensity of excitation light source. Unlike the photochromic property commonly observed in solution-state polymer materials, solid-state perovskite materials with photochromic behavior might open wide applications in consumer products and electronic devices. In the next part, we report on a reversible photoluminescence (PL) peak in iodide-based organic-inorganic lead halide perovskite materials under a 2-photon absorption process, while tuning the excitation wavelength. Intriguingly, two shorter wavelength peaks are visible and become prominent when the excitation photon energy is being tuned in the high energy spectrum, while laser power is remained constant. The same phenomenon of reversible PL peak is also observed in various iodine-based organic-inorganic halides as well as all-inorganic perovskite single crystals and polycrystals. We attribute to the reversible PL peak phenomenon to the photoinduced structural deformation and the associated change in the optical bandgap of iodide perovskites under the femtosecond laser excitation. Our findings will introduce a degree of freedom in future research as well as adding functionalities to optoelectronic applications in these emerging perovskite materials-based devices.

Catalysis by Metals on Perovskite-Type Oxides

Perovskites are currently on everyone’s lips and have made it in high-impact scientific journals because of the revolutionary hybrid organic–inorganic lead halide perovskite materials for solar cells [...]

Materials Discovery of Stable and Nontoxic Halide Perovskite Materials for High‐Efficiency Solar Cells

AbstractTwo critical limitations of organic–inorganic lead halide perovskite materials for solar cells are their poor stability in humid environments and inclusion of toxic lead. In this study, high‐throughput density functional theory (DFT) methods are used to computationally model and screen 1845 halide perovskites in search of new materials without these limitations that are promising for solar cell applications. This study focuses on finding materials that are comprised of nontoxic elements, stable in a humid operating environment, and have an optimal bandgap for one of single junction, tandem Si‐perovskite, or quantum dot–based solar cells. Single junction materials are also screened on predicted single junction photovoltaic (PV) efficiencies exceeding 22.7%, which is the current highest reported PV efficiency for halide perovskites. Generally, these methods qualitatively reproduce the properties of known promising nontoxic halide perovskites that are either experimentally evaluated or predicted from theory. From a set of 1845 materials, 15 materials pass all screening criteria for single junction cell applications, 13 of which are not previously investigated, such as (CH3NH3)0.75Cs0.25SnI3, ((NH2)2CH)Ag0.5Sb0.5Br3, CsMn0.875Fe0.125I3, ((CH3)2NH2)Ag0.5Bi0.5I3, and ((NH2)2CH)0.5Rb0.5SnI3. These materials, together with others predicted in this study, may be promising candidate materials for stable, highly efficient, and nontoxic perovskite‐based solar cells.

Probe-induced resistive switching memory based on organic-inorganic lead halide perovskite materials

Abstract In this paper we demonstrate a resistive storage device with CH3NH3PbI3−xClx/FTO structure which stores information in two levels of resistance states induced by electrical probe excitation. The perovskite layer is formed on a FTO coated glass by a single-step solution spin coating method in the air. We study the effects of different probe materials on the memory cell behavior including silver epoxy, copper and graphite. The device with silver probe shows a bipolar resistive switching behavior with 106 on/off resistance ratio in the forming process. The fabricated probe-based memory cell shows a minimum endurance of 104 cycles and a minimum retention time of 2 × 103 s. These experimental results confirm that organic-inorganic lead halide perovskite (OILHP) materials are a potential candidate to be used as a storage medium for probe based storage memories. This study provides a better understanding of resistive switching mechanism in organic-inorganic lead halide perovskites thin films that can be useful for understanding of the future probe-based beyond Moore's law memory devices.

Halide Perovskite Photovoltaics: Background, Status, and Future Prospects.

The photovoltaics of organic-inorganic lead halide perovskite materials have shown rapid improvements in solar cell performance, surpassing the top efficiency of semiconductor compounds such as CdTe and CIGS (copper indium gallium selenide) used in solar cells in just about a decade. Perovskite preparation via simple and inexpensive solution processes demonstrates the immense potential of this thin-film solar cell technology to become a low-cost alternative to the presently commercially available photovoltaic technologies. Significant developments in almost all aspects of perovskite solar cells and discoveries of some fascinating properties of such hybrid perovskites have been made recently. This Review describes the fundamentals, recent research progress, present status, and our views on future prospects of perovskite-based photovoltaics, with discussions focused on strategies to improve both intrinsic and extrinsic (environmental) stabilities of high-efficiency devices. Strategies and challenges regarding compositional engineering of the hybrid perovskite structure are discussed, including potentials for developing all-inorganic and lead-free perovskite materials. Looking at the latest cutting-edge research, the prospects for perovskite-based photovoltaic and optoelectronic devices, including non-photovoltaic applications such as X-ray detectors and image sensing devices in industrialization, are described. In addition to the aforementioned major topics, we also review, as a background, our encounter with perovskite materials for the first solar cell application, which should inspire young researchers in chemistry and physics to identify and work on challenging interdisciplinary research problems through exchanges between academia and industry.

Revealing lattice and photocarrier dynamics of high-quality MAPbBr3 single crystals by far infrared reflection and surface photovoltage spectroscopy

Hybrid organic-inorganic lead halide perovskite materials show great promise in a number of optoelectronic applications, including solar cells, light emitting diodes, and photodetectors. Understanding their intrinsic material properties is critical to enhancing device performance and enabling innovative material and device designs. Here, we study lattice dynamics using far-infrared (FIR) reflectance and photogenerated carrier dynamics using surface photovoltage (SPV) measurements on high-quality methylammonium lead bromide (MAPbBr3) single crystals. FIR reflectance shows three coherent infrared-active phonon modes between 40 and 200 cm−1 that result in reststrahlen bands with much higher peak reflectance than has been previously reported. The phonon mode strength and damping are comparable to classical oxide perovskite single crystals. However, the effects of defects on photogenerated carrier recombination are still evident in SPV measurements. By performing SPV over different spectral ranges, we are able to separate the effects of surface and bulk defects on the recombination dynamics of photogenerated charge carriers. We further apply SPV measurements to obtain the minority carrier (electron) diffusion length for the MAPbBr3 crystal. This study demonstrates that both FIR reflectance and SPV measurements provide useful information on the electromagnetic response properties of halide perovskite single crystals.

Enhanced piezoelectric output performance via control of dielectrics in Fe2+-incorporated MAPbI3 perovskite thin films: Flexible piezoelectric generators

We report a high-performance flexible piezoelectric generator (PEG) that was based on organic-inorganic lead halide perovskite materials and is operated by controlling the dielectric constant via the partial substitution of Pb2+ with Fe2+ in MAPbI3. The partial replacement of Pb2+ with Fe2+ improved both the morphology and crystallinity of MAPb1-xFexI3 (0.01 ≤ x ≤ 0.50) films that undergo a tetragonal-cubic phase transition above an incorporated concentration of Fe2+ (x > 0.07). In addition, the phase transition temperatures of MAPb1-xFexI3 (0.01 ≤ x ≤ 0.07) films linearly decreased as a function of incorporated concentration, which resulted in a transition temperature for MAPb1-xFexI3 (x = 0.07) of ~ 45.5 ± 1.5 °C. The dielectric properties as a function of incorporated concentration at room temperature suggested that MAPb1-xFexI3 (x = 0.07) exhibited a dielectric constant of ~107 and a dissipation factor of 0.02 at 100 kHz. The MAPb1-xFexI3 (x = 0.07) films exhibited a low leakage current density of ~ 10−6 at a high applied electric field of 40 kV/cm, and the resultant remanent polarization from saturated ferroelectric P-E hysteresis loops was ~ 1.6 µC/cm2. The MAPb1-xFexI3 (x = 0.07) flexible PEG improved output performance by ~ 7.29 V and current density by ~ 0.88 µA/cm2 after poling at 30 kV/cm. This was sufficient to instantly light a commercial light-emitting diode (LED) without a storage device. This approach provides a framework that enhances the output performance of organic-inorganic metal halide perovskite materials-based piezoelectric energy harvesters, which could help pave the road to viable, self-powered, wearable electronics.

Robust Cesium Lead Halide Perovskite Microcubes for Frequency Upconversion Lasing

AbstractHalide perovskite nanomaterials have recently attracted a lot of attention in the nanoscale laser research field, especially two‐photon pumped lasing in halide perovskite nanomaterials has been considered as an ideal alternative strategy to achieve frequency upconversion. However, the poor stability of current organic–inorganic lead halide perovskite materials hinder their further practical applications. Herein, facile solution‐processed cesium lead halide perovskite CsPbX3 (X = Br, I, or Cl) microcubes with low‐threshold lasing, high quality, enhanced stability, and excellent wavelength tunability are reported. These as‐prepared CsPbX3 microcubes display excellent structure stability under ambient conditions for several months and they are found to be more robust than their organic–inorganic counterparts. The smooth end facets and wavelength‐comparable dimensions make these microcubes promising for high‐quality laser cavities in three dimensions. Fabry–Perot lasing is demonstrated in CsPbX3 microcubes, the process of which is investigated by dynamic emission. In addition, tunable amplified spontaneous emission is achieved with low threshold under both one‐ and two‐photon excitation, which can maintain a stable emission for over 10 hours under continuous intense laser shots in ambient atmosphere. The findings suggest that solution‐processed all‐inorganic perovskite microcubes can be used as excellent gain medium for frequency upconversion lasers, which would offer a new platform for nonlinear photoelectric devices.

Effect of disorder on transport properties in a tight-binding model for lead halide perovskites

The hybrid organic-inorganic lead halide perovskite materials have emerged as remarkable materials for photovoltaic applications. Their strengths include good electric transport properties in spite of the disorder inherent in them. Motivated by this observation, we analyze the effects of disorder on the energy eigenstates of a tight-binding model of these materials. In particular, we analyze the spatial extension of the energy eigenstates, which is quantified by the inverse participation ratio. This parameter exhibits a tendency, and possibly a phase transition, to localization as the on-site energy disorder strength is increased. However, we argue that the disorder in the lead halide perovskites corresponds to a point in the regime of highly delocalized states. Our results also suggest that the electronic states of mixed-halide materials tend to be more localized than those of pure materials, which suggests a weaker tendency to form extended bonding states in the mixed-halide materials and is therefore not favourable for halide mixing.

High-performance piezoelectric nanogenerators composed of formamidinium lead halide perovskite nanoparticles and poly(vinylidene fluoride)

Formamidinium lead halide perovskite nanoparticles (FAPbBr3 NPs), because of their prominent piezoelectric properties, have drawn increasing attention in the fields of piezoelectric applications. Remarkable enhancement of piezoelectric power output is achieved from a piezoelectric composite nanogenerator by combining the FAPbBr3 NPs with poly(vinylidene fluoride) (PVDF) polymer. The FAPbBr3 NPs @ PVDF composite based piezoelectric nanogenerators show the highest outstanding outputs with voltage of 30V and current density of 6.2μAcm−2 for organic-inorganic lead halide perovskite material based devices. The improved performance can be ascribed to the using of PVDF, piezoelectric polymer as matrix, as well as the homogeneous distribution of FAPbBr3 NPs with enhanced stress on piezoelectric nanoparticles. The alternating energy generated from the nanogenerator can be utilized to charge a capacitor through a bridge rectifier and light up a commercial light-emitting diode (LED). Our obtained results open the feasibility of organic-inorganic lead halide perovskite materials for the design and development of high-efficiency energy harvesting applications.

Flexible Piezoelectric Nanocomposite Generators Based on Formamidinium Lead Halide Perovskite Nanoparticles

Organic–inorganic lead halide perovskite materials have recently attracted much attention in the field of optoelectronic devices. Here, a hybrid piezoelectric nanogenerator based on a composite of piezoelectric formamidinium lead halide perovskite (FAPbBr3) nanoparticles and polydimethylsiloxane polymer is fabricated. Piezoresponse force spectroscopy measurements reveal that the FAPbBr3 nanoparticles contain well‐developed ferroelectric properties with high piezoelectric charge coefficient (d33) of 25 pmV−1. The flexible device exhibits high performance with a maximum recordable piezoelectric output voltage of 8.5 V and current density of 3.8 μA cm−2 under periodically vertical compression and release operations. The alternating energy generated from nanogenerators can be used to charge a capacitor and light up a red light‐emitting diode through a bridge rectifier. This result innovatively expands the feasibility of organic–inorganic lead halide perovskite materials for application in a wide variety of high‐performance energy harvesting devices.

Lasing in robust cesium lead halide perovskite nanowires

The rapidly growing field of nanoscale lasers can be advanced through the discovery of new, tunable light sources. The emission wavelength tunability demonstrated in perovskite materials is an attractive property for nanoscale lasers. Whereas organic-inorganic lead halide perovskite materials are known for their instability, cesium lead halides offer a robust alternative without sacrificing emission tunability or ease of synthesis. Here, we report the low-temperature, solution-phase growth of cesium lead halide nanowires exhibiting low-threshold lasing and high stability. The as-grown nanowires are single crystalline with well-formed facets, and act as high-quality laser cavities. The nanowires display excellent stability while stored and handled under ambient conditions over the course of weeks. Upon optical excitation, Fabry-Pérot lasing occurs in CsPbBr3 nanowires with an onset of 5 μJ cm(-2) with the nanowire cavity displaying a maximum quality factor of 1,009 ± 5. Lasing under constant, pulsed excitation can be maintained for over 1 h, the equivalent of 10(9) excitation cycles, and lasing persists upon exposure to ambient atmosphere. Wavelength tunability in the green and blue regions of the spectrum in conjunction with excellent stability makes these nanowire lasers attractive for device fabrication.

Spray PEDOT:PSS coated perovskite with a transparent conducting electrode for low cost scalable photovoltaic devices

Organic–inorganic lead halide perovskite materials are an attractive candidate for low-cost thin-film photovoltaics but in order to successfully rival other technologies, it is critical to focus research on addressing the potential bottlenecks to commercialisation. The conventional hole transporter spiro-OMeTAD and evaporated gold contact are unsuitable for commercialisation due to the cost. This study introduces a method for fabricating perovskite devices without spiro-OMeTAD. Instead, PEDOT:PSS was applied directly to the perovskite material using a carefully controlled spray process. The water hyphen containing PEDOT:PSS used was spray coated onto the perovskite film with careful drying to provide a 55-nm-thick interlayer between the perovskite and the electrode providing hole collection. XRD analysis showed that by controlled application, it was possible to avoid water-induced perovskite degradation. The device was completed using a previously demonstrated transparent conducting adhesive electrode based on vertically orientated channels of PEDOT:PSS within an acrylic adhesive instead of evaporated gold. Fully fabricated devices gave comparable performance to those without spiro-OMeTAD.