Hybrid Lead Iodide Perovskites Research Articles

Phonon Properties and Lattice Dynamics of Two- and Tri-Layered Lead Iodide Perovskites Comprising Butylammonium and Methylammonium Cations-Temperature-Dependent Raman Studies.

Hybrid lead iodide perovskites are promising photovoltaic and light-emitting materials. Extant literature data on the key optoelectronic and luminescent properties of hybrid perovskites indicate that these properties are affected by electron-phonon coupling, the dynamics of the organic cations, and the degree of lattice distortion. We report temperature-dependent Raman studies of BA2MAPb2I7 and BA2MA2Pb3I10 (BA = butylammonium; MA = methylammonium), which undergo two structural phase transitions. Raman data obtained in broad temperature (360-80 K) and wavenumber (1800-10 cm-1) ranges show that ordering of BA+ cations triggers the higher temperature phase transition, whereas freezing of MA+ dynamics occurs below 200 K, leading to the onset of the low-temperature phase transition. This ordering is associated with significant deformation of the inorganic sublattice, as evidenced by changes observed in the lattice mode region. Our results show, therefore, that Raman spectroscopy is a very valuable tool for monitoring the separate dynamics of different organic cations in perovskites, comprising "perovskitizer" and interlayer cations.

Methyl-ammonium lead iodide hybrid perovskite thin film as active material for energy conversion devices

The use of hybrid halide Perovskites is helping us get closer to our aim of completely selfsufficient structures in terms of energy production. Preparation of a device of photoactive material CH3NH3PbI3 {FTO (Fluorine-doped tin Oxide)/ CH3NH3PbI3/SpiroOMeTAD/Al} for the photovoltaic applications has been described in this article. Producing a homogeneous thin film through the use of lower temperature, processedsolution devices with one-step spin coating processes is an essential stage in the fabrication process. To generate the thin films on the FTO-substrate, the one-step spin coating approach was utilized for the deposition of the precursor solution, which consisted of methylammonium iodide and lead iodide in a molar ratio of 3:1. This technique was employed to prepare the thin films. The FESEM technique was utilized to carry out the investigation of the surface morphology of this thin layer. In addition, the essential parameters of this device, like barrier height, saturation current, current density, ideality factor, carrier mobility, resistance, carrier lifetime, and capacitance have been computed using current-voltage (I-V) characteristics and the impedance spectroscopy technique. A laser with a power of 20 milliwatts and a wavelength of 532 nanometers was used to light the gadget. The current conduction mechanism exhibits ohmic behavior at a low voltage, while at medium voltages, TFSCLC is the mechanism that regulates charge transportation. Despite the fact that TCSCLC is demonstrated at higher voltages. The TCSCLC model was used to conduct an investigation of the hole's mobility.

Weak X-Ray to Visible Lights Detection Enabled by a 2D Multilayered Lead Iodide Perovskite with Iodine-Substituted Spacer.

Broadband photodetectors (PDs) with low detection limits hold significant importance to next-generation optoelectronic devices. However, simultaneously detecting broadband (i.e., X-ray to visible regimes) and weak lights in a single semiconducting material remains highly challenging. Here, by alloying iodine-substituted short-chain cations into the 3D FAPbI3 (FA = formamidine), a new 2D bilayered lead iodide hybrid perovskite, (2IPA)2 FAPb2 I7 (1, 2IPA = 2-iodopropylammonium), that enables addressing this challenge is reported. Such a 2D multilayered structure and lead iodide composition jointly endow 1 with a minimized dark current (6.04 pA), excellent electrical property, and narrow bandgap (2.03eV), which further gives it great potential for detecting broadband weak lights. Consequently, its high-quality single crystal PDs exhibit remarkable photoresponses to weak ultraviolet-visible lights (377-637nm) at several tens of nW cm-2 with high responsivities (>102 mA W-1 ) and significant detectivities (>1012 Jones). Moreover, 1 has an excellent X-ray detection performance with a high sensitivity of 438 µC Gy-1 cm-2 and an ultralow detection limit of 20 nGy s-1 . These exceptional attributes make 1 a promising material for broadband weak lights detection, which also sheds light on future explorations of high-performance PDs based on 2D hybrid perovskites.

Differing Effects of Mixed A-Site Composition on the Properties of Hybrid Lead Iodide Perovskites

Halide perovskites (HPs) appeared as a revolutionary class of relevant optoelectronic materials. Optimizing these materials involves developing mixed formulations currently used in many of the most efficient HP-based devices. Mixing A-site organic cations has been a widely used strategy to achieve the desired characteristics in these perovskites. Few of the reported works were devoted to understanding the effects of different organic cations on the properties of the resulting HPs. In the present work, we report a detailed study on the structural, thermal, and electrical properties and degradation assays in HPs with mixing A-site organic cations at the MAPbI3, FA0.10MA0.90PbI3, GA0.10MA0.90PbI3, and GA0.05FA0.05MA0.90PbI3 compositions. The results show that the charge transport properties change consistently with the A-site cation size. However, the structure and phase transitions are unusually affected by the composition, suggesting that other characteristics of substituent cations are relevant to the behavior of the resulting materials. Finally, thermal degradation tests reveal that, contrary to general expectations, not all mixed compositions are more stable than their related pure HPs. More than that, the order of degradation kinetics may also depend on the type of substituent cation. The results elucidate the particularities of each type of organic cation on the properties of mixed perovskites and advance knowledge about these relevant materials.

Effect of Electron–Phonon Coupling on the Color Purity of Two-Dimensional Ruddlesden–Popper Hybrid Lead Iodide Perovskites

Two-dimensional (2D) lead halide perovskites have become a class of promising luminescent materials due to their excitonic nature and excellent environmental stability. However, it seems counterintuitive that the 2D perovskites possess extremely narrow emission, while at the same time they have been reported to reveal strong electron–phonon coupling, which generally leads to significant emission broadening. Here, the main factors affecting the electron–phonon coupling of 2D perovskites are investigated to interpret the observed light emission with full width at half maximum as small as 12.7 nm (∼58 meV) at room temperature (RT). We demonstrate that the electron–phonon coupling in 2D perovskites is structure-dependent, and coupling with the phonon mode in the organic layer rather than the inorganic one plays an important role in the broadening of emission. This scenario is evidenced by temperature-dependent photoluminescence spectroscopy and structural change of 2D perovskites with various bulky organic cations (L-series) and different numbers of inorganic layers (n-series). Our results suggest that the electron–phonon coupling in L-series 2D perovskites could be weak below 250 K, which leads to a small broadening, thus mainly contributing to high color purity at RT. While for the n-series, the increase of inorganic layer number induces a monotonic increase of the line width broadening in the low-temperature region, which reduces the color purity at RT.

Anion influence on electronic and optical properties of several iodobismuthates

Complex lead iodide hybrid perovskites show high photovoltaic efficiency, but their use in solar cells may be limited due to Pb toxicity and its great bioavailability because of its solubility in water. Iodobismuthates can emerge as a promising alternative for solar cells, having no toxicity and exhibiting high stability in relation to the oxidation in air. To know if the iodoplumbates can be substituted with less toxic iodobismuthates without reducing the photovoltaic efficiency, microscopic contributions to the absorption coefficients are analyzed for two compounds. The absorption coefficients were obtained from first principles. To identify and quantify the most important contributions to the optical gaps, the absorption coefficients are split as an exact many-species expansion. From the results, the electronic and optical gaps are different. Additionally, the optical gap and the optical properties are rather insensitive to the cationic structure.

Revealing the impact of organic spacers and cavity cations on quasi-2D perovskites via computational simulations

Two-dimensional hybrid lead iodide perovskites based on methylammonium (MA) cation and butylammonium (BA) organic spacer—such as {hbox {BA}_{2}hbox {MA}_{n-1}hbox {Pb}_{n}hbox {I}_{3n+1}}—are one of the most explored 2D hybrid perovskites in recent years. Correlating the atomistic profile of these systems with their optoelectronic properties is a challenge for theoretical approaches. Here, we employed first-principles calculations via density functional theory to show how the cation partially canceled dipole moments through the {{hbox {NH}_{3}}^{+}} terminal impact the structural/electronic properties of the {hbox {Pb}_{n}hbox {I}_{3n+1}} sublattices. Even though it is known that at high temperatures, the organic cation assumes a spherical-like configuration due to the rotation of the cations inside the cage, our results discuss the correct relative orientation according to the dipole moments for ab initio simulations at 0 K, correlating well structural and electronic properties with experiments. Based on the combination of relativistic quasiparticle correction and spin-orbit coupling, we found that the MA horizontal-like configuration concerning the inorganic sublattice surface leads to the best relationship between calculated and experimental gap energy throughout n = 1, 2, 3, 4, and 5 number of layers. Conversely, the dipole moments cancellation (as in BA-MA aligned-like configuration) promotes the closing of the gap energies through an electron depletion mechanism. We found that the anisotropy rightarrow isotropy optical absorption conversion (as a bulk convergence) is achieved only for the MA horizontal-like configuration, which suggests that this configuration contribution is the majority in a scenario under temperature effects.

Probing the Genuine Carrier Dynamics of Semiconducting Perovskites under Sunlight.

Understanding the nature of photogenerated carriers and their subsequent dynamics in semiconducting perovskites is important for the development of solar cell materials and devices. However, most ultrafast dynamic measurements on perovskite materials were conducted under high carrier densities, which likely obscures the genuine dynamics under low carrier densities in solar illumination conditions. In this study, we presented a detailed experimental study of the carrier density-dependent dynamics in hybrid lead iodide perovskites from femtosecond to microsecond using a highly sensitive transient absorption (TA) spectrometer. From the dynamic curves with low carrier density in the linear response range, we observed two fast trapping processes that occurred in less than 1 ps and tens of picoseconds, attributed to the shallow traps, and two slow decays with lifetimes of hundreds of nanoseconds and longer than 1 μs, related to the trap-assisted recombination and trapping at deep traps. Further TA measurements clearly show that PbCl2 passivation can effectively reduce both shallow and deep trap densities. These results provide insights into the intrinsic photophysics of semiconducting perovskites with direct implications for photovoltaic and optoelectronic applications under sunlight.

Thick-Layer Lead Iodide Perovskites with Bifunctional Organic Spacers Allylammonium and Iodopropylammonium Exhibiting Trap-State Emission.

The nature of the organic cation in two-dimensional (2D) hybrid lead iodide perovskites tailors the structural and technological features of the resultant material. Herein, we present three new homologous series of (100) lead iodide perovskites with the organic cations allylammonium (AA) containing an unsaturated C═C group and iodopropylammonium (IdPA) containing iodine on the organic chain: (AA)2MAn-1PbnI3n+1 (n = 3-4), [(AA)x(IdPA)1-x]2MAn-1PbnI3n+1 (n = 1-4), and (IdPA)2MAn-1PbnI3n+1 (n = 1-4), as well as their perovskite-related substructures. We report the in situ transformation of AA organic layers into IdPA and the incorporation of these cations simultaneously into the 2D perovskite structure. Single-crystal X-ray diffraction shows that (AA)2MA2Pb3I10 crystallizes in the space group P21/c with a unique inorganic layer offset (0, <1/2), comprising the first example of n = 3 halide perovskite with a monoammonium cation that deviates from the Ruddlesden-Popper (RP) halide structure type. (IdPA)2MA2Pb3I10 and the alloyed [(AA)x(IdPA)1-x]2MA2Pb3I10 crystallize in the RP structure, both in space group P21/c. The adjacent I···I interlayer distance in (AA)2MA2Pb3I10 is ∼5.6 Å, drawing the [Pb3I10]4- layers closer together among all reported n = 3 RP lead iodides. (AA)2MA2Pb3I10 presents band-edge absorption and photoluminescence (PL) emission at around 2.0 eV that is slightly red-shifted in comparison to (IdPA)2MA2Pb3I10. The band structure calculations suggest that both (AA)2MA2Pb3I10 and (IdPA)2MA2Pb3I10 have in-plane effective masses around 0.04m0 and 0.08m0, respectively. IdPA cations have a greater dielectric contribution than AA. The excited-state dynamics investigated by transient absorption (TA) spectroscopy reveal a long-lived (∼100 ps) trap state ensemble with broad-band emission; our evidence suggests that these states appear due to lattice distortions induced by the incorporation of IdPA cations.

Experimental study of heat transfer in thin-film perovskite-based structures using a low-coherent tandem interferometry

The heat transfer in an archetypal system solar cell/environment was analyzed, in which the solar cell was a thin-film multilayer structure with a hybrid lead-iodide perovskite photoabsorber. The temperature field was mathematically modeled and heat maps of the cell at various irradiation intensities were calculated. It was found that the heating by a diffuse insolation does not exceed the threshold critical for the stability of the perovskite phase owing to dissipation into the environment, with the temperature maximum close to half of the overall thickness of the structure. Keywords: perovskite, thin film, heat transfer, solar cells, diffuse insolation.

Chalcogenide Perovskites and Perovskite-Based Chalcohalide as Photoabsorbers: A Study of Their Properties, and Potential Photovoltaic Applications.

In 2015, a class of unconventional semiconductors, Chalcogenide perovskites, remained projected as possible solar cell materials. The MAPbI3 hybrid lead iodide perovskite has been considered the best so far, and due to its toxicity, the search for potential alternatives was important. As a result, chalcogenide perovskites and perovskite-based chalcohalide have recently been considered options and potential thin-film light absorbers for photovoltaic applications. For the synthesis of novel hybrid perovskites, dimensionality tailoring and compositional substitution methods have been used widely. The study focuses on the optoelectronic properties of chalcogenide perovskites and perovskite-based chalcohalide as possibilities for future photovoltaic applications.

Defect-Induced Narrowband Light Emission from a 2D Hybrid Lead Iodide Perovskite

Defect-Induced Narrowband Light Emission from a 2D Hybrid Lead Iodide Perovskite

Revealing phase evolution mechanism for stabilizing formamidinium-based lead halide perovskites by a key intermediate phase

Revealing phase evolution mechanism for stabilizing formamidinium-based lead halide perovskites by a key intermediate phase

Synthesis of Hybrid Lead Iodide Perovskite Thin Film by Two-Step Method Modified with a Double Dipping Circle to Control Its Crystallization and Morphology to Improve Solar Cells’ Performance

Crystallization and morphology of perovskite film played an important role to obtain efficient performance of perovskite solar cells. This study is aimed at optimizing the fabrication of hybrid organic–inorganic lead iodide perovskite layer by a two-step method modified by a double dip coating process which enables to control the perovskite crystallization and morphology. The duration time of each circle for the step of dipping PbI2 film to methylammonium iodide solution was varied from 90 to 240 second. The obtained perovskite films were characterized by X-ray diffraction to evaluate the transformation of PbI2 reactant to the perovskite product and its crystallization, by scanning electron microscopy to observe its morphology. Then, the perovskite films were implemented in functional perovskite solar cell devices followed by current–voltage characterization. Results showed that the perovskite was formed via an equilibrium process which reached an optimum transformation of PbI2 to the product after 2 × 150 second circle dip coating, and its morphology was smooth with the least voids. The solar cell devices fabricated at the optimum conditions achieved a comparable performance of about 14%.

Halide Perovskites: Suppressed Lattice Disorder for Large Emission Enhancement and Structural Robustness in Hybrid Lead Iodide Perovskite Discovered by High‐Pressure Isotope Effect (Adv. Funct. Mater. 9/2021)

In article number 2009131, Gang Liu and co-workers conduct high-pressure isotope research to discover a significantly suppressed lattice disorder realized by H/D substitution in hybrid halide perovskites, which reveals large emission enhancement and strong structural robustness in isotope-functionalized perovskite materials. The CD3ND3PbI3-based device also exhibits slower degradation of photovoltaic performance, which is promising for better materials-by-design and more stable photovoltaic applications.

Экспериментальное исследование процессов теплопереноса в тонкопленочных структурах на основе перовскитов методом низкокогерентной тандемной интерферометрии

The heat transfer in an archetypal system ‘solar cell/environment’ was analyzed, in which the solar cell was a thin-film multilayer structure with a hybrid lead-iodide perovskite photoabsorber. The temperature field was mathematically modeled and heat maps of the cell at various irradiation intensities were calculated. It was found that the heating of the structure by a diffuse insolation has a maximum at about half of the overall thickness, but it does not exceed the threshold critical for the stability of the perovskite phase owing to dissipation into the environment.

Layer-by-Layer Structural Identification of 2D Ruddlesden–Popper Hybrid Lead Iodide Perovskites by Solid-State NMR Spectroscopy

Application of two-dimensional (2D) organic–inorganic hybrid halide perovskites in optoelectronic devices requires a detailed understanding of the local structural features including the Pb–I bondi...

Kinetic Molecular Cationic Control of Defect-Induced Broadband Light Emission in 2D Hybrid Lead Iodide Perovskites.

In this study, we examine the effects of changing organic cation concentrations on the efficiency and photophysical implications of exciton trapping in two-dimensional hybrid lead iodide self-assembled quantum wells (SAQWs). We show that increasing the concentration of alkyl and aryl ammonium cations causes the formation of SAQWs at a liquid-liquid interface to possess intense, broadband subgap photoluminescence (PL) spectra. Electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopic studies suggest that materials formed under these cation concentrations possess morphologies consistent with inhibited crystallization kinetics but exhibit qualitatively similar bulk chemical bonding to nonluminescent materials stabilized in the same structure from precursor solutions containing lower cation concentrations. Temperature- and power-dependent PL spectra suggest that the broadband subgap light emission stems from excitons self-trapped at defect sites, which we assign as edge-like, collective I vacancies using a simple model of the chemical equilibrium driving material self-assembly. These results suggest that changes to the availability of molecular cations can suitably control the light emission properties of self-assembled hybrid organic-inorganic materials in ways central to their applicability in lighting technologies.

Suppressed Lattice Disorder for Large Emission Enhancement and Structural Robustness in Hybrid Lead Iodide Perovskite Discovered by High‐Pressure Isotope Effect

AbstractThe soft nature of organic–inorganic halide perovskites renders their lattice particularly tunable to external stimuli such as pressure, undoubtedly offering an effective way to modify their structure for extraordinary optoelectronic properties. Here, using the methylammonium lead iodide as a representative exploratory platform, it is observed that the pressure‐driven lattice disorder can be significantly suppressed via hydrogen isotope effect, which is crucial for better optical and mechanical properties previously unattainable. By a comprehensive in situ neutron/synchrotron‐based analysis and optical characterizations, a remarkable photoluminescence (PL) enhancement by threefold is convinced in deuterated CD3ND3PbI3, which also shows much greater structural robustness with retainable PL after high peak‐pressure compression–decompression cycle. With the first‐principles calculations, an atomic level understanding of the strong correlation among the organic sublattice and lead iodide octahedral framework and structural photonics is proposed, where the less dynamic CD3ND3+ cations are vital to maintain the long‐range crystalline order through steric and Coulombic interactions. These results also show that CD3ND3PbI3‐based solar cell has comparable photovoltaic performance as CH3NH3PbI3‐based device but exhibits considerably slower degradation behavior, thus representing a paradigm by suggesting isotope‐functionalized perovskite materials for better materials‐by‐design and more stable photovoltaic application.

Hybrid Lead Iodide Perovskites with Mixed Cations of Thiourea and Methylamine, From One Dimension to Three Dimensions.

Hybrid halide perovskites featuring as new materials of high-performance solar cells have attracted great research interest. The temperature-dependent dimensional transition of halide perovskites is a crucial handle in the preparation of perovskite films. Only the small cations of methylammonium (MA) or formamidinium (FA) have been involved for most of the dimensional transition materials. In this work, thiourea (tu) is introduced into hybrid halide materials. A new series of 1D ribbonlike hybrid lead iodides with tu and MA cations are reported that were crystallographically characterized as MAn(Htu)n+1PbnI4n+1 (n = 1-4 denoted as 1-4, respectively; in 1, MA is replaced by tu). The width of the perovskite ribbon increases from one PbI6 octahedron to four corner-fused octahedra. Compounds 2 and 3 can be turned into a black 3D perovskite after annealing. This is an unusual mixed MA-tu hybrid halide perovskite system, in which the tu molecule plays an important role in manipulating the dimensions and their photoconductive properties. Scanning electron microscopy of the blackened sample shows that there are a lot of regular vent holes on the smooth crystal surface with sizes of hundreds of nanometers. The tunable structures and porous crystals might be advantageous in the sense of material modulation.