perovskite and methylamine

The structural stability of the extensively studied organic-inorganic hybrid methylammonium tetrel halide perovskite semiconductors, MATtX

Topics: Hydrogen; Models, Molecular; Oxides

This paper reports numerical modeling of perovskite solar cell which has been knotted with Distributed Bragg Reflector pairs to extract high energy efficiency. The geometry of the proposed cells is simulated with three different kinds of perovskite materials including CH3NH3PbI3, CH3NH3PbBr3, and CH3NH3SnI3. The toxic perovskite material based on Lead iodide and lead bromide appears to be more efficient as compared to non-toxic perovskite material. The executed simulated photovoltaic parameters with the highest efficient structure are open circuit voltage = 1.409 (V), short circuit current density = 24.09 mA/cm2, fill factor = 86.18%, and efficiency = 24.38%. Moreover, a comparison of the current study with different kinds of structures has been made and surprisingly our novel geometry holds enhanced performance parameters that are featured with back reflector pairs (Si/SiO2). The applied numerical approach and presented designing effort of geometry are beneficial to obtain results that have the potential to address problems with less efficient thin-film solar cells.

Topics: Algorithms; Calcium Compounds; Iodides; Lead; Methylamines; Models, Theoretical; Oxides; Solar Energy; Titanium

Hybrid, e.g., organic inorganic, perovskites from the type methylammonium lead iodide CH

Topics: Automation; Calcium Compounds; Iodides; Lead; Luminescent Measurements; Materials Science; Methylamines; Oxides; Spectrum Analysis; Temperature; Titanium

In recent years, flexible perovskite solar cells have drawn tremendous attention in the field of wearable devices, and optimization of perovskite composition plays an important role in improving film quality and photophysical properties. At present, some researchers have only studied A-site organic cations mixing or X-site halide anions mixing in the ABX

Topics: Amidines; Calcium Compounds; Carbon; Cold Temperature; Electrodes; Methylamines; Oxides; Solar Energy; Titanium

A new solvent system for PbI

Topics: Acetone; Calcium Compounds; Crystallization; Methylamines; Oxides; Protons; Solubility; Solvents; Spectrum Analysis; Titanium

Metal halide perovskites have generated interest across many fields for the impressive optoelectronic properties achievable in films produced using facile solution-processing techniques. Previous research has revealed the colloidal nature of perovskite precursor inks and established a relationship between the colloid distribution and the film optoelectronic quality. Yet, the identity of colloids remains unknown, hindering our understanding of their role in perovskite crystallization. Here, we investigate precursor inks of the prototypical methylammonium lead triiodide perovskite using cryo-electron microscopy (cryo-EM) and show, for the first time, that the colloids are neither amorphous nor undissolved lead iodide, as previously speculated, but are a crystalline, non-perovskite material. We identify this as a perovskite precursor phase and discuss this as a potential means to understanding the role of chloride in processing. This work establishes cryo-EM as a viable technique to elucidate the nature of colloids in perovskite inks, a vital step toward a fundamental understanding of thin-film crystallization.

Topics: Calcium Compounds; Colloids; Cryoelectron Microscopy; Crystallization; Halogens; Ink; Methylamines; Oxides; Titanium

The protonated perovskite-like titanate H

Topics: Butylamines; Calcium Compounds; Chemistry Techniques, Synthetic; Chemistry, Organic; Hot Temperature; Intercalating Agents; Lanthanoid Series Elements; Magnetic Resonance Spectroscopy; Methanol; Methylamines; Microscopy, Electron, Scanning; Oxides; Oxygen; Spectrophotometry, Infrared; Spectrum Analysis, Raman; Temperature; Thermogravimetry; Titanium; X-Ray Diffraction

We present a Raman study on the phase transitions of organic/inorganic hybrid perovskite materials, CH₃NH₃PbX₃ (X = I, Br), which are used as solar cells with high power conversion efficiency. The temperature dependence of the Raman bands of CH₃NH₃PbX₃ (X = I, Br) was measured in the temperature ranges of 290 to 100 K for CH₃NH₃PbBr₃ and 340 to 110 K for CH₃NH₃PbI₃. Broad ν₁ bands at ~326 cm

Topics: Calcium Compounds; Halogens; Lead; Methylamines; Oxides; Phase Transition; Spectrum Analysis, Raman; Temperature; Titanium

In inverted perovskite solar cells (PSCs), high-quality perovskite film grown on hole-transporting material (HTM) with pinhole-free coverage and a large grain size is crucial for high efficiency. Here, we report on the growth of pinhole-free and large grain CH

Topics: Calcium Compounds; Crystallization; Electricity; Hydrophobic and Hydrophilic Interactions; Iodides; Lead; Methylamines; Oxides; Solar Energy; Spectrophotometry, Ultraviolet; Tin Compounds; Titanium; X-Ray Diffraction

It is commonly believed that excess PbI

Topics: Calcium Compounds; Iodides; Lead; Methylamines; Oxides; Titanium

Topics: Calcium Compounds; Crystallization; Electric Power Supplies; Iodides; Kinetics; Lead; Methylamines; Oxides; Solar Energy; Titanium

Topics: Calcium Compounds; Electric Power Supplies; Iodides; Lead; Methylamines; Oxides; Solar Energy; Titanium; Tungsten Compounds

A new broadband-emitting 2 D hybrid organic-inorganic perovskite (CyBMA)PbBr

Topics: Calcium Compounds; Cyclohexanes; Luminescence; Methylamines; Models, Molecular; Molecular Conformation; Oxides; Titanium

Methylammonium lead iodide perovskite (MAPI) is a promising material for highly efficient photovoltaic devices. However, it suffers from photooxidation, which imposes strict requirements for its protection from oxygen during processing and operation. A hindered amine light stabilizer (HALS) has been found to exert a stabilization effect on methylammonium iodide (MAI) and MAPI against photooxidation. The HALS prevents the degradation of MAI by inhibiting the oxidation of iodide to iodine. Chemical modification of HALS allows its incorporation in MAPI films, which extends the resistivity of MAPI against photodegradation in ambient air from a couple of hours to several days, while causing no significant changes in key properties, such as optical absorption and charge transport. These results represent an important advance in the stabilization of MAPI against decomposition and demonstrate for the first time that antioxidants improve the stability of MAPI.

Topics: Calcium Compounds; Drug Stability; Iodides; Lead; Light; Methylamines; Oxides; Oxygen; Titanium

An understanding of charge-carrier recombination processes is essential for the development of hybrid metal halide perovskites for photovoltaic applications. We show that typical measurements of the radiative bimolecular recombination constant in CH

Topics: Calcium Compounds; Diffusion; Electric Conductivity; Electron Transport; Iodides; Lead; Methylamines; Nanotechnology; Oxides; Photochemical Processes; Photons; Semiconductors; Terahertz Spectroscopy; Titanium

Organo-lead halide perovskites have recently attracted great interest for potential applications in thin-film photovoltaics and optoelectronics. Herein, we present a protocol for the fabrication of this material via the low-pressure vapor assisted solution process (LP-VASP) method, which yields ~19% power conversion efficiency in planar heterojunction perovskite solar cells. First, we report the synthesis of methylammonium iodide (CH3NH3I) and methylammonium bromide (CH3NH3Br) from methylamine and the corresponding halide acid (HI or HBr). Then, we describe the fabrication of pinhole-free, continuous methylammonium-lead halide perovskite (CH3NH3PbX3 with X = I, Br, Cl and their mixture) films with the LP-VASP. This process is based on two steps: i) spin-coating of a homogenous layer of lead halide precursor onto a substrate, and ii) conversion of this layer to CH3NH3PbI3-xBrx by exposing the substrate to vapors of a mixture of CH3NH3I and CH3NH3Br at reduced pressure and 120 °C. Through slow diffusion of the methylammonium halide vapor into the lead halide precursor, we achieve slow and controlled growth of a continuous, pinhole-free perovskite film. The LP-VASP allows synthetic access to the full halide composition space in CH3NH3PbI3-xBrx with 0 ≤ x ≤ 3. Depending on the composition of the vapor phase, the bandgap can be tuned between 1.6 eV ≤ Eg ≤ 2.3 eV. In addition, by varying the composition of the halide precursor and of the vapor phase, we can also obtain CH3NH3PbI3-xClx. Films obtained from the LP-VASP are reproducible, phase pure as confirmed by X-ray diffraction measurements, and show high photoluminescence quantum yield. The process does not require the use of a glovebox.

Topics: Calcium Compounds; Lead; Methylamines; Oxides; Solutions; Titanium; Vapor Pressure

Organometal halide perovskites show promising features for cost-effective application in photovoltaics. The material instability remains a major obstacle to broad application because of the poorly understood degradation pathways. Here, we apply simultaneous luminescence and electron microscopy on perovskites for the first time, allowing us to monitor in situ morphology evolution and optical properties upon perovskite degradation. Interestingly, morphology, photoluminescence (PL), and cathodoluminescence of perovskite samples evolve differently upon degradation driven by electron beam (e-beam) or by light. A transversal electric current generated by a scanning electron beam leads to dramatic changes in PL and tunes the energy band gaps continuously alongside film thinning. In contrast, light-induced degradation results in material decomposition to scattered particles and shows little PL spectral shifts. The differences in degradation can be ascribed to different electric currents that drive ion migration. Moreover, solution-processed perovskite cuboids show heterogeneity in stability which is likely related to crystallinity and morphology. Our results reveal the essential role of ion migration in perovskite degradation and provide potential avenues to rationally enhance the stability of perovskite materials by reducing ion migration while improving morphology and crystallinity. It is worth noting that even moderate e-beam currents (86 pA) and acceleration voltages (10 kV) readily induce significant perovskite degradation and alter their optical properties. Therefore, attention has to be paid while characterizing such materials using scanning electron microscopy or transmission electron microscopy techniques.

Topics: Calcium Compounds; Electrons; Iodides; Lead; Methylamines; Microscopy, Atomic Force; Microscopy, Electron, Scanning; Oxides; Titanium

Organic-inorganic perovskites such as CH3NH3PbI3 are promising materials for a variety of optoelectronic applications, with certified power conversion efficiencies in solar cells already exceeding 21%. Nevertheless, state-of-the-art films still contain performance-limiting non-radiative recombination sites and exhibit a range of complex dynamic phenomena under illumination that remain poorly understood. Here we use a unique combination of confocal photoluminescence (PL) microscopy and chemical imaging to correlate the local changes in photophysics with composition in CH3NH3PbI3 films under illumination. We demonstrate that the photo-induced 'brightening' of the perovskite PL can be attributed to an order-of-magnitude reduction in trap state density. By imaging the same regions with time-of-flight secondary-ion-mass spectrometry, we correlate this photobrightening with a net migration of iodine. Our work provides visual evidence for photo-induced halide migration in triiodide perovskites and reveals the complex interplay between charge carrier populations, electronic traps and mobile halides that collectively impact optoelectronic performance.

Topics: Calcium Compounds; Iodides; Iodine; Lead; Light; Luminescent Measurements; Methylamines; Microscopy, Confocal; Oxides; Spectrometry, Mass, Secondary Ion; Titanium

The solution processing of pinhole-free methylammonium lead triiodide perovskite-C

Topics: Calcium Compounds; Drug Stability; Electric Power Supplies; Electron Transport; Fluorine; Fullerenes; Glass; Methylamines; Oxides; Solar Energy; Solvents; Tin Compounds; Titanium

In the past few years, the efficiency of solar cells based on hybrid organic-inorganic perovskites has exceeded the level needed for commercialization. However, existing perovskites solar cells (PSCs) suffer from several intrinsic instabilities, which prevent them from reaching industrial maturity, and stabilizing PSCs has become a critically important problem. Here we propose to stabilize PSCs chemically by strengthening the interactions between the organic cation and inorganic anion of the perovskite framework. In particular, we show that replacing the methylammonium cation with alternative protonated cations allows an increase in the stability of the perovskite by forming strong hydrogen bonds with the halide anions. This interaction also provides opportunities for tuning the electronic states near the bandgap. These mechanisms should have a universal character in different hybrid organic-inorganic framework materials that are widely used.

Topics: Calcium Compounds; Drug Stability; Electrons; Halogens; Hydrogen Bonding; Methylamines; Models, Molecular; Molecular Conformation; Oxides; Titanium

We report herein the discovery of methylamine (CH3NH2) induced defect-healing (MIDH) of CH3NH3PbI3 perovskite thin films based on their ultrafast (seconds), reversible chemical reaction with CH3NH2 gas at room temperature. The key to this healing behavior is the formation and spreading of an intermediate CH3NH3PbI3⋅xCH3NH2 liquid phase during this unusual perovskite-gas interaction. We demonstrate the versatility and scalability of the MIDH process, and show dramatic enhancement in the performance of perovskite solar cells (PSCs) with MIDH. This study represents a new direction in the formation of defect-free films of hybrid perovskites.

Topics: Calcium Compounds; Electric Power Supplies; Gases; Methylamines; Oxides; Phase Transition; Solar Energy; Titanium

The crystal morphology of organolead trihalide perovskite (OTP) light absorbers can have profound influence on the perovskite solar cells (PSCs) performance. Here we have used a combination of conventional transmission electron microscopy (TEM) and high-resolution TEM (HRTEM), in cross-section and plan-view, to characterize the morphologies of a solution-processed OTP (CH3NH3PbI3 or MAPbI3) within mesoporous TiO2 scaffolds and within capping and planar layers. Studies of TEM specimens prepared with and without the use of focused ion beam (FIB) show that FIBing is a viable method for preparing TEM specimens. HRTEM studies, in conjunction with quantitative X-ray diffraction, show that MAPbI3 perovskite within mesoporous TiO2 scaffold has equiaxed grains of size 10-20 nm and relatively low crystallinity. In contrast, the grain size of MAPbI3 perovskite in the capping and the planar layers can be larger than 100 nm in our PSCs, and the grains can be elongated and textured, with relatively high crystallinity. The observed differences in the performance of planar and mesoscopic-planar hybrid PSCs can be attributed in part to the striking differences in their perovskite-grain morphologies.

Topics: Calcium Compounds; Methylamines; Microscopy, Electron, Transmission; Organometallic Compounds; Oxides; Particle Size; Porosity; Solar Energy; Titanium; X-Ray Diffraction

The Rashba effect is spin degeneracy lift originated from spin-orbit coupling under inversion symmetry breaking and has been intensively studied for spintronics applications. However, easily implementable methods and corresponding materials for directional controls of Rashba splitting are still lacking. Here, we propose organic-inorganic hybrid metal halide perovskites as 3D Rashba systems driven by bulk ferroelectricity. In these materials, it is shown that the helical direction of the angular momentum texture in the Rashba band can be controlled by external electric fields via ferroelectric switching. Our tight-binding analysis and first-principles calculations indicate that S = 1/2 and J = 1/2 Rashba bands directly coupled to ferroelectric polarization emerge at the valence and conduction band edges, respectively. The coexistence of two contrasting Rashba bands having different compositions of the spin and orbital angular momentum is a distinctive feature of these materials. With recent experimental evidence for the ferroelectric response, the halide perovskites will be, to our knowledge, the first practical realization of the ferroelectric-coupled Rashba effect, suggesting novel applications to spintronic devices.

Topics: Calcium Compounds; Computer Simulation; Crystallization; Electronics; Iron; Methylamines; Models, Chemical; Nanostructures; Organic Chemicals; Oxides; Titanium