Methyl Ammonium Research Articles

Cation Migration in Physically Paired 2D and 3D Lead Halide Perovskite Films

Abstract2D/3D interfaces provide long‐term stability for the operation of metal halide perovskite solar cells. However, the cation migration under heat and light can disturb the interface and create a graded cation interface. This study has now probed the cation migration by physically pairing X2PbI4 (X = butylammonium BA, oleylammonium OA, or phenethylammonium PEA) 2D film and (CH3NH3, MA)PbI3 3D film at different temperatures and recording changes in the absorption and emission spectra. The migration of the methyl ammonium cation toward the 2D film slowly transforms the n = 1 layered phase into n = 2 and 3 layered phases. The 3D film, on the other hand, exhibits relatively small changes, as the inclusion of spacer cation has little effect on its phase. The apparent activation energy determined from the temperature‐dependent cation migration kinetics (Ea = 29– 50 kJ mol−1) indicates alkyl ammonium cations such as butyl ammonium migrate more readily into the 3D layer than aromatic cations such as PEA. The ease of migration of spacer cations between physically paired films suggests that the varied composition at the interface should be considered while evaluating the effectiveness of the 2D/3D design strategy for improving the performance of perovskite solar cells.

Influence of irradiation energy and damage coefficient on performance of CH3NH3PI3 photocell

An organic–inorganic hybrid perovskite as a light-absorbing layer has become a key material in many laminated-structures used in photon sensing devices. Some of these devices are referred to as Organic–inorganic hybrid perovskite (OIHP)-based devices. In recent days, OIHP applications have sky-rocketed in the world of flexible photo-electronics. Due to the higher radiation tolerances, OIHP-based solar cells have been recommended for terrestrial applications which is an application that require low fabrication costs that combines lightweight materials. However, it has been noticed that when it is used in extra-terrestrial environments, these photo cell devices experience premature failures once they interact with fast multispectral radiations in terrestrial spaces. Due to these premature failures, a similar solar cell from an (OIHP)-based perovskite material of methyl ammonium lead iodide (CH3NH3PI3) was investigated as an observer layer under a multi-spectral simulated illumination. After simulation, data for the expected photocurrent flowing through junction components on a glass substrate coated with a thin layer of Titanium dioxide (TiO 2) film was obtained. The influence of energy of irradiation on damage coefficients, current density, photovoltage and I–V characteristic profile curves were determined and investigated. Some general common macroscopic parameters for photon sensing were analyzed on three dimensions (3D) to determining the minority charge carriers and their induced photo-voltages with respect to junction recombination velocities. The obtained computed macroscopic parameters were incorporated into the Quite Universal Circuit Simulator software for simulation. It was established that damage coefficient influenced the I–V curve and an accumulation of charge carriers magnifies the probability of plasmons initiating degradation of the absorber layer. The atoms in the CH3NH3Pl3 crystal lattice system uniformly recoils at resonance and transport the maximum charge carriers across the P-N junction capable of creating a significant damage concentrated within a few micrometer ranges on the surface that may even extend between 0.39 to about 1.01 micrometers in size. This paper therefore evaluates the influence of irradiation energy and damage coefficient in a hybrid CH3NH3PI3 mono-facet crystal structure on exposure to multi-spectral illumination at varied irradiation energies.

Exploring the performance of perovskite solar cells with dual hole transport layers via SCAPS-1D simulation

The potential of perovskite solar cells (PSCs) to produce high efficiency (over 25 %) is well known, but the poor stability of these solar cells is still a concern for practical applications. Thus, improving the stability is essential for furthering the development of PSCs. To address this issue, researchers found that incorporating inorganic materials into the hole transport layers (HTLs) can improve the stability of PSCs, yet charge recombination at the interface between the perovskite and inorganic HTLs can still reduce the efficiency of the PSCs. This study simulated the performance and mechanism of methyl ammonium lead iodide (MAPbI3) PSCs with a dual HTL using Solar Cell Capacitance Simulator-one Dimension (SCAPS-1D). A dual HTL formed by combining Spiro-OMeTAD (spiro), a highly efficient hole transport material, and copper zinc tin sulfide (CZTS), a highly stable hole transport material, leads to a PSC with a power conversion efficiency (PCE) of 23.47 % and significantly improved stability. Simulation results of the electric field at the interfaces of PSCs indicated that the PSC with spiro/CZTS as dual HTL have enhanced charge separation and reduced recombination. Furthermore, the simulation results have also revealed the influence of different parameters, such as absorber thickness, absorber defect density, HTL thickness, HTL/absorber interface defects, temperature, series resistance, and shunt resistance, on solar cell’s characteristics.

Solid Electrolyte Interphase Formation in Tellurium Iodide Perovskites during Electrochemistry and Photoelectrochemistry.

Halide perovskites are promising photoelectrocatalytic materials. Their further development requires understanding of surface processes during electrochemistry. Thin films of tellurium-based vacancy-ordered perovskites with formula A2TeI6, A = Cs, methylammonium (MA), were deposited onto transparent conducting substrates using aerosol-assisted chemical vapor deposition. Thin film stability as electrodes and photoelectrodes was tested in dichloromethane containing tetrabutylammonium PF6 (TBAPF6). Using photoemission spectroscopy, we show that the formation of a solid electrolyte interphase on the surface of the Cs2TeI6, consisting of CsPF6, enhances the stability of the electrode and allows extended chopped-light chronoamperometry measurements at up to 1.1 V with a photocurrent density of 16 μA/cm2. In contrast, (CH3NH3)2TeI6 does not form a passivating layer and rapidly degrades upon identical electrochemical treatment. This demonstrates the importance of surface chemistry in halide perovskite electrochemistry and photoelectrocatalysis.

Methyl ammonium iodide via novel PECVD process for the growth of 2-step vacuum based perovskite (MAPbI3) thin films

MAPbI3 thin films were grown via 2-step vacuum based processes by depositing methyl ammonium iodide (MAI) layer as first step using plasma enhanced chemical vapour deposition (PECVD) technique and then depositing lead iodide (PbI2) layer over it as second step using RF-sputtering technique. To the best of our knowledge MAI layer was deposited for the first time by PECVD technique. MAI solution for PECVD process and PbI2 target for sputtering process were made to deposit these two layers under optimized plasma conditions for the growth of MAPbI3 thin films. Characterization techniques like UV-Vis-NIR spectroscopy and Photoluminescence spectroscopy were performed to study the optical properties. Powder-XRD (PXRD) and glancing incidence XRD (GIXRD) were performed to study structural properties. SEM and cross-SEM were performed for morphological study to view top-view and cross-sectional view of the deposited MAPbI3 perovskite thin film. Perovskite thin films deposited on silicon wafer have been used as perovskite/silicon heterojunction photodiode exhibiting critical performance parameters such as rectifying ratio of 1.58 × 104 at 1.0 V, photo-sensitivity value 7.46 × 102 at light intensity 100 mw/cm2 without biasing.

Lead-sulfur interaction induced damp and water stability in pure formamidinium lead triiodide

Research efforts in various multitudes have been demonstrated to stabilize methylammonium (MA)- and bromide (Br)-free formamidinium lead triiodide (FAPI) perovskite thin films. Despite these commendable efforts, pure FAPI perovskite thin film is prone to critical phase-transition issues due to its thermodynamically stable non-perovskite phase (2H). Here, in this work, we propose a rational additivization strategy to overcome this challenge. Our multifunctional ammonium salt containing a sulfur heteroatom shifts the thermodynamic stability from the 2H phase to an intermediate phase closer to the cubic phase. Along with the high crystallinity, micron-sized grains with preferred (00h) facet orientation stem the Pb…S interaction to offer exceptional stability against high relative humidity, direct water incursion, and shelf-life aging. Our findings through experimental and theoretical studies substantiate the role of Pb…S interaction in stabilizing the perovskite cubic phase and the stoichiometric distribution of elemental components.

Quasi 2D Ruddlesden–Popper perovskite thin film electrode for supercapacitor application: Role of diffusion and capacitive process in charge storage mechanism

Hybrid halide perovskites are the most widely explored materials in the photovoltaic field. Recently they have been investigated for energy storage applications owing to their unique conductivity. Most reports on supercapacitor applications of halide perovskites are based on Methyl ammonium lead iodide (MAPbI3) and Methyl ammonium lead bromide (MAPbBr3) compounds. These halides are prone to degradation owing to external environmental parameters. Hence, one must look for other stable alternative halides. In this scenario, materials that can yield significant results with better stability are Quasi 2D perovskites, which combine the properties of both 3D and 2D perovskites. We successfully synthesized and characterized 4-Fluorobenzylammine hydroiodide spacer cation-based quasi 2D perovskite in this study. A detailed study was carried out on the effect of the precursor concentration and annealing temperature on the morphology and vertical growth of quasi-2D perovskite. An in-depth analysis of these perovskites' graded, phase-segregated growth was performed. Furthermore, we prepared a composite electrode from a mixture of quasi-2D perovskite with acetylene carbon black to obtain better performance. Our results show a maximum specific capacitance of 8.67 F g−1 from Cyclic Voltammetry curves. Further from the Galvanostatic Charge Discharge (GCD) curves, we obtained a capacitance of 3.39 F g−1. It is the highest value obtained for perovskite thin-film based supercapacitor electrode. The material displayed a low charge transfer resistance indicating a better conducting property, and displayed energy and power density of 170 mWh kg−1 and 109 W kg−1, respectively. Further, the contribution of capacitance and diffusion limited process in the charge storage mechanism of these electrodes were quantified. The electrodes could retain 91% capacitance after working for 1000 cycles, emerging as potential energy storage material for the future.

Contactless quasi-steady-state photoconductance (QSSPC) characterization of metal halide perovskite thin films

We apply the contactless quasi-steady-state photoconductance (QSSPC) method to co-evaporated methyl ammonium lead iodide (MAPbI3) perovskite thin-films. Using an adapted calibration for ultralow photoconductances, we extract the injection-dependent carrier lifetime of the MAPbI3 layer. The lifetime is found to be limited by radiative recombination at the high injection densities applied during the QSSPC measurement, enabling the extraction of the electron and hole mobility sum in the MAPbI3 using the known coefficient of radiative recombination of MAPbI3. Combining the QSSPC measurement with transient photoluminescence measurements, performed at much lower injection densities, we obtain the injection-dependent lifetime curve over several orders of magnitude. From the resulting lifetime curve, we determine the achievable open-circuit voltage of the examined MAPbI3 layer.

Self‐Healing and ‐Repair of Nanomechanical Damages in Lead Halide Perovskites

AbstractRecovery from damage in materials helps extend their useful lifetime and of devices that contain them. Given that the photodamages in HaP materials and based devices are shown to recover, the question arises if this also applies to mechanical damages, especially those that can occur at the nanometer scale, relevant also in view of efforts to develop flexible HaP‐based devices. Here, this question is addressed by poking HaP single crystal surfaces with an atomic force microscope (AFM) tip under both ultra‐high vacuum (UHV) and variably controlled ambient water vapor pressure conditions. Sequential in situ AFM scanning allowed real‐time imaging of the morphological changes at the damaged sites. Using methylammonium (MA) and cesium (Cs) variants for A‐site cations in lead bromide perovskites, the experiments show that nanomechanical damages on methylammonium lead bromide (MAPbBr3) crystals heal an order of magnitude faster than Cs‐based ones in UHV. However, surprisingly, under ≥40% RH conditions, cesium lead bromide (CsPbBr3) shows MAPbBr3‐like fast healing kinetics. Direct evidence for ion solvation on CsPbBr3 is presented, leading to the formation of a surface hydration layer. The results imply that moisture improves the ionic mobility of degradation components and leads to water‐assisted improved healing, i.e., repair of nanomechanical damages in the HaPs.

Effect of carbon quantum dots and Zn2+ ion on perovskite solar cells

Perovskite solar cells (PSCs) have a great attention due to their remarkable performance and a high-quality perovskite film is necessary to achieve high power conversion efficiency (PCE). The effect of carbon quantum dots (CQDs) and Zn2+ ions on perovskite layer of methyl ammonium lead iodide (MAPbI3) was investigated. The optical, structural, and morphological properties of perovskite films with different Zn2+ ratios and CQDs contents were investigated. It was observed that 1% ZnCl2 /0.05 mg/mL CQDs perovskite film composed of uniform grains distribution, complete surface coverage with negligible pinholes, and a larger grain size of 1.8 μm. In addition, it was found that increasing CQDs contents to 0.1 and 0.25 mg/mL enlarged the grain size to ~ 4.2 μm. Moreover, the incorporation of CQDs enhanced crystallinity and grain size. Consequently, these improvements were reflected on the solar cell performance and the efficiency of PSCs with additive of 1% ZnCl2-0.05 mg/mL CQDs was improved from 4.21 to 8.08%.

Device simulation of CH3NH3PbI3-xClx based mixed halide perovskite thin film solar cells

Perovskite solar cells are an emerging area of study in photovoltaics research due to their low cost fabrication and high efficiency. In this paper, the numerical simulation of FTO/CdS/CH3NH3PbI3-xClx/CuI/Au device performance was investigated using solar cell capacitance simulator (SCAPS-1D). Here, mixed halide perovskite, Chloride (Cl) doped methyl ammonium lead iodide (CH3NH3PbI3-xClx), is used as perovskite light absorber layer due to good thermal stability, film quality and tunable bandgap property. In this present solar cell configuration CdS is used as buffer layer and CuI as hole transport layer (HTL). The effect of absorber layer thickness, operating temperature and different HTL’s were also analyzed on device performance. By varying the thickness of the absorber layer from 0.1 to 1.0 µm,the optimum thickness was found at 0.7 µm. In addition to this different HTL’s CuI, Spiro-OMeTAD and Cu2O were used in simulation and CuI gives best results compared to others. With optimized parameters, the proposed device achieves a PCE of 27.19%, FF of 87.88%, JSC of 23.86 mA/cm2 and VOC of 1.29 V. These optimized results will be used for the fabrication of an CH3NH3PbI3-xClx perovskite thin film solar cell.

Improving the efficiency and stability in a MAPbI3 perovskite solar cell using dimensionally engineered PbS quantum dot passivation layer

Using a dimensionally engineered nano film of lead sulphide (PbS) above/below the methyl ammonium lead tri-iodide (MAPbI3) as a passivation layer in a planar inverted perovskite solar cell (PSC), we have shown that the power conversion efficiency (PCE) can increase at least by 3% compared to the reference MAPbI3 inverted perovskite solar cell. This improvement of 3% in efficiency using a PbS nano layer is better than any other reference reported in the literature. Further, with the incorporation of PbS nano film the fill factor (FF) showed a significant enhancement, reaching over 0.81. In addition, the effects of perovskite layer thickness, PbS layer thickness, and different optical parameters like absorbance, reflectance, transmittance, and temperature on the PCE are also investigated. The results of this investigation seem to be important for the realisation of low cost and more efficient solar cells based on PbS nano film and perovskite materials.

Composition, additive, and process engineering of halide perovskite green photodetector for enhanced responsivity and detectivity

Si-based materials have been successfully adapted for photodiode (PD) sensing applications. However, their micrometer-scale thickness requirement and parasitic light absorption limit color discrimination. In this study, we developed halide-perovskite-based thin films through composition engineering and process optimization for green-light sensing with high detectivity and responsivity. First, composition engineering studies, i.e., ratio control of methylammonium (MA) and formamidinium (FA) precursors and subsequent annealing condition optimization, were conducted to control the bandgap and phase formation of green-targeted perovskite absorber films. Next, we studied the effect of the CH3NH3Cl (MACl) additive on reducing the dark current and enhancing phase stability. Notably, space-charge-limited current measurements revealed that MACl could effectively reduce the trap density. Furthermore, simultaneous optimization of the cationic site composition, annealing conditions, and additive significantly affected the perovskite film morphology, phase stability, and defect formation, enabling the fabrication of high-performance green PDs. Our optimized, green-targeted PD exhibits a superior responsivity of 55.24 A·W−1 (under 7.17 × 10−7 W·cm−2 excitation), an average external quantum efficiency of 86%, and a high on/off ratio, thereby providing a feasible approach for future PD commercialization.

Mixed Organic Cations Promote Ambient Light-Induced Formation of Metallic Lead in Lead Halide Perovskite Crystals.

One major concern toward the performance and stability of halide perovskite-based optoelectronic devices is the formation of metallic lead that promotes nonradiative recombination of charge carriers. The origin of metallic lead formation is being disputed whether it occurs during the perovskite synthesis or only after light, electron, or X-ray beam irradiation or thermal annealing. Here, we show that the quantity of metallic lead detected in perovskite crystals depends on the concentration and composition of the precursor solution. Through a controlled crystallization process, we grew black-colored mixed dimethylammonium (DMA)/methylammonium (MA) lead tribromide crystals. The black color is suggested to be due to the presence of small lead clusters. Despite the unexpected black coloring, the crystals show higher crystallinity and less defect density with respect to the standard yellow-colored DMA/MAPbBr3 crystals, as indicated by X-ray rocking curve and dark current measurements, respectively. While the formation of metallic lead could still be induced by external factors, the precursor solution composition and concentration can facilitate the formation of metallic lead during the crystallization process. Our results indicate that additional research is required to fully understand the perovskite precursor solution chemistry.

Simulation study of Zinc/cobalt doped methyl ammonium lead iodide for solar cells

Simulation study of Zinc/cobalt doped methyl ammonium lead iodide for solar cells

Sequential Co-Passivation in InAs Colloidal Quantum Dot Solids Enables Efficient Near-Infrared Photodetectors.

III-V colloidal quantum dots (CQDs) are promising materials for optoelectronic applications, for they avoid heavy metals while achieving absorption spanning the visible to the infrared (IR). However, the covalent nature of III-V CQDs requires the development of new passivation strategies to fabricate conductive CQD solids for optoelectronics: this work shows herein that ligand exchanges, previously developed in II-VI and IV-VI quantum dots and employing a single ligand, do not fully passivate CQDs, and that this curtails device efficiency. Guided by density functional theory (DFT) simulations, this work develops a co-passivation strategy to fabricate indium arsenide CQD photodetectors, an approach that employs the combination of X-type methyl ammonium acetate (MaAc) and Z-type ligands InBr3 . This approach maintains charge carrier mobility and improves passivation, seen in a 25% decrease in Stokes shift, a fourfold reduction in the rate of first-exciton absorption linewidth broadening over time-under-stress, and leads to a doubling in photoluminescence (PL) lifetime. The resulting devices show 37% external quantum efficiency (EQE) at 950nm, the highest value reported for InAs CQD photodetectors.

Using Imidazolium in the Construction of Hybrid 2D and 3D Lead Bromide Pseudoperovskites

The field of hybrid organic–inorganic perovskite materials continues to attract the interest of the scientific community due to their fascinating properties and the plethora of promising applications in photovoltaic and optoelectronic devices. To enhance the efficiency and stability of perovskite-based devices, it is essential to discover novel compounds but also to investigate their various physicochemical, structural, and thermal properties. In this work, we report the synthesis and structural characterization of two novel hybrid lead bromide perovskites, combining the imidazolium cation (IMI) with methylammonium (MA) or formamidinium (FA) cations. The isolated polycrystalline powders were studied with X-ray powder diffraction (XPRD) and were formulated as (IMI)(MA)Pb2Br6, a 3D structure consisting of dimers of face-sharing octahedra linked in corner-sharing mode, and (IMI)(FA)PbBr4, a 2D (110) oriented layer structure with zig-zag corner-sharing octahedra. The thermal stability of (IMI)(MA)Pb2Br6 and (IMI)(FA)PbBr4 was investigated with thermogravimetric (TG) and differential scanning calorimetry (DSC) experiments which showed that both compounds are chemically stable (at least) up to 250 °C. Variable-temperature X-ray diffractometric (VT-XRD) studies of (IMI)(FA)PbBr4 highlighted a structural modification occurring above 100 °C, that is a phase transformation from triclinic to orthorhombic, via an elusive monoclinic phase.

A Novel Multi‐Functional Thiophene‐Based Organic Cation as Passivation, Crystalline Orientation, and Organic Spacer Agent for Low‐Dimensional 3D/1D Perovskite Solar Cells

AbstractRecently, the mixed‐dimensional (3D/2D or 3D/1D) perovskite solar cells using small organic spacers have attracted interest due to their outstanding long‐term stability. Here, a new type of thiophene‐based organic cation 2‐(thiophene‐2yl‐)pyridine‐1‐ium iodide (ThPyI), which is used to fabricate mixed‐dimensional 3D/1D perovskite solar cells, is presented. The ThPyI‐based 1D perovskitoid is applied as a passivator on top of a 3D methyl ammonium lead iodide (MAPI) to fabricate surface‐passivated 3D/1D perovskite films or added alone into the 3D perovskite precursor to generate bulk‐passivated 3D MAPI. The 1D perovskitoid acts as a passivating agent at the grain boundaries of surface‐passivated 3D/1D, which improves the power conversion efficiency (PCE) of the solar cells. Grazing incidence wide‐angle X‐ray scattering (GIWAXS) studies confirm that ThPyI triggers the preferential orientation of the bulk MAPI slabs, which is essential to enhance charge transport. Champion bulk‐passivated 3D and surface‐passivated 3D/1D devices yield 14.10% and 19.60% PCE, respectively. The bulk‐passivated 3D offers favorable stability, with 84% PCE retained after 2000 h without encapsulation. This study brings a new perspective to the design of organic spacers having a different binding motif and a passivation strategy to mitigate the impact of defects in hybrid 3D/1D perovskite solar cells.

N-Cetyl-N,N,N-tri methyl ammonium bromide based Tin(IV) Phosphate, A New Surfactant based Hybrid Ion Exchanger: Synthesis, Ion exchange and Physico-chemical Characterization

N-Cetyl-N,N,N-tri methyl ammonium bromide based Tin (IV) Phosphate has been reported as a new class of hybrid ion exchanger. It has been characterized by some physico-chemical studies such as FTIR analysis, SEM study and elemental analysis. Its method of synthesis along with ion exchange characterization has also been reported in this study including ion exchange capacity, concentration study, elution study, recycling study and thermal stability. The antimicrobial activity of N-Cetyl-N, N, N-tri methyl ammonium bromide based Tin (IV) Phosphate on some microorganisms such as Staph Awrens, E. coli ESS 2231, Protect vulgaris and Aspergillus fumigatus has also been studied to prove the antimicrobial nature of the reported material. Based on the above study it has been concluded that the present material can be of great importance in environmental pollution control.

Numerical simulation and experimental study of methyl ammonium bismuth iodide absorber layer based lead free perovskite solar cells.

Recent years have witnessed a tremendous surge in the design and fabrication of lead-(Pb) free perovskite or perovskite-like materials for the construction of perovskite solar cells. The simulation and fabrication of Pb free perovskite-like structures based perovskite solar cells are of great significance. In present study, we have simulated methyl ammonium bismuth iodide (MA3Bi2I9) based perovskite solar cells using solar cell capacitance software (SCAPS). The thickness of the electron-transport layer, hole-transport layer and absorber layer were optimized via SCAPS. The simulated perovskite solar cells (FTO/TiO2/MA3Bi2I9/spiro-OMeTAD/Au) with optimized conditions demonstrated good power conversion efficiency of 14.07% with reasonable open circuit voltage of 1.34 V via SCAPS. In further studies, we also fabricated perovskite solar cells under controlled humidity which showed power conversion efficiency of 1.31%.