Methylammonium Lead Halide Perovskite Research Articles

Rashba and Dresselhaus effects in doped methylammonium lead halide perovskite MAPbI3.

Inorganic-organic lead halide perovskites, particularly methylammonium lead halide (MAPbI3) perovskite, have been regarded as promising materials for optoelectronics and spintronics. However, the practical applications of these perovskites are limited by lead toxicity and instability under air and pressure. This study investigates the substitution of Pb with Sn and Ge in cubic MAPbI3 perovskite. The properties of the resulting hybrid perovskites are compared using state-of-the-art first-principles-based methodologies, viz., density functional theory (DFT) with generalized gradient approximation (PBE) and hybrid functional (HSE06), in conjunction with spin-orbit coupling (SOC). Here, we mainly study the Rashba-Dresselhaus (RD) effect, which arises due to two major mechanisms: (i) the breaking of inversion symmetry (static and dynamic) and (ii) SOC, originating from the presence of heavy elements. We find significant spin-splitting effects in the conduction band minimum and valence band maximum for hybrid perovskites. To gain a deeper understanding of the observed spin-splitting, the spin textures are analyzed, and Rashba coefficients are calculated. We find that the Dresselhaus effect comes into play in substituted hybrid structures in addition to the usual Rashba effect observed in the pristine compound. Additionally, we observe that the strength of Rashba spin-splitting is substantially tuned by the application of uniaxial strain (±5%). Moreover, certain hybrid perovskites exhibit mechanical stability and ductility, making them potential candidates in perovskite-based optoelectronics and spintronics applications.

Effect of Chloride Incorporation on the Intermediate Phase and Film Morphology of Methylammonium Lead Halide Perovskites.

The influence of chloride integration on perovskite film deposition, encompassing both the structures of intermediate phases and the properties of the final films, was explored. Our methodology involved the fabrication of perovskite intermediate-phase films with varying concentrations of methylammonium chloride (MACl). Subsequently, we conducted an analysis employing X-ray diffraction and Rietveld refinement, incorporating the March-Dollase correction, to gain insights into how chloride-induced intermediate phases impact film morphology. Remarkably, a distinct preferred orientation was observed in the (020) lattice plane perpendicular to the substrate surface, and this orientation was found to be directly correlated to the MACl concentration. This distinctive arrangement of chloride-induced intermediate-phase complexes facilitated controlled crystallization, leading to highly oriented crystals and an improved film morphology. As a consequence, perovskite solar cell devices incorporating chloride-containing methylammonium lead iodide achieved a power conversion efficiency exceeding 20%. These findings suggest a crucial link between the preferred orientation observed in the final chlorine-derived perovskite films and the intermediate-phase structure formed during the initial stages of perovskite formation. These results suggest a profound impact of intermediate phase compositions and crystal structures on perovskite formation, emphasizing the importance of a comprehensive understanding of these factors to enable precise control over ideal structures and the subsequent transformation into high-quality perovskite films.

High performance self-powered photodetector based on CuBi2O4/MAPbI3 heterostructure

Methylammonium lead halide perovskites have garnered significant consideration for application in numerous optoelectronic devices due to their remarkable physical properties. However, the photoconductivity performance of these organolead halide perovskites is still lower than the conventional Si optoelectronic devices such as photodetectors, which is one of the major barriers to their practical applications. Combining suitable inorganic semiconductors with organolead halide perovskite may provide an alternative route for fabricating photodetectors that are expected to have improved photosensitivity. Here, a high performance self-power photodetector based on CuBi2O4/CH3NH3PbI3 (MAPbI3) heterojunction was synthesized under ambient conditions using the spin-coating technique. The severely reduced peak intensity in PL spectra and short decay time of CuBi2O4/MAPbI3 compared to MAPbI3 indicate efficient charge separation at the interface. The self-powered CuBi2O4/MAPbI3 showed photovoltaic-like effect with a maximum open circuit voltage Vo of ∼0.34 ± 0.02 V under the illumination of 365 nm light with 8.63 μW/cm2 power density. Moreover, CuBi2O4/MAPbI3 heterojunction base photodetector exhibits a high responsivity of ∼0.39 ± 0.04 W/A, a detectivity of ∼1.79 ± 0.17 × 1011 Jones, a fast response speed (rise time ∼ 36 ± 0.14 ms, fall time 81 ± 0.21 ms) and self-powering ability compared to that of MAPbI3 only device. This work offers an effective and feasible way to improve the performance of MAPbI3-based devices for photoelectronic applications.

Molecularly imprinted fluorescence assay based on lead halide perovskite quantum dots for determination of benzo(a)pyrene.

Molecularly imprinted polymers with methylammonium lead halide perovskite quantum dots (MIP@MAPbBr3 PQDs) have been prepared and applied tothe determination of benzo(a)pyrene (BaP) for the first time. The photoluminescence (PL) of MIP@MAPbBr3 PQDs was enhanced due to the surface passivation of defects by BaP. PL excitation and emission spectra, X-ray diffraction, Fourier transform infrared, and time-resolved PL studies suggest that the interaction between MIP@MAPbBr3 PQDs and BaP is a dynamic process. After MIP@MAPbBr3 PQDs were incubated with BaP, the benzene ring in the molecular structure of BaP can interact with MIP@MAPbBr3 PQDs through π electrons, which reduces non-radiative recombination of MIP@MAPbBr3 PQDs and lengthens excited state lifetime. The PL intensity of the MIP@MAPbBr3 PQDs-BaP system was monitored at 520 nm with 375 nm excitation. Under optimized conditions, the PL intensity of MIP@MAPbBr3 PQDs is linear with the concentration of BaP in the 10 to 100 ng·mL-1 range, with a detection limit of 1.6 ng·mL-1. The imprinting factor was 3.9, indicating excellent specificity of MIP@MAPbBr3 PQDs for BaP. The MIP@MAPbBr3 PQDs were subsequently applied to the PL analysis of BaP in sunflower seed oil, cured meat, and grilled fish samples, achieving recoveries from 79.3 to 107%, and relative standard deviations below 10%. This molecularly imprinted fluorescence assay improves the selectivity of BaP in complex mixtures and could be extended to other analytes.

Surface Restructuring of Zeolite-Encapsulated Halide Perovskite to Activate Lattice Oxygen Oxidation for Water Electrolysis.

Metal-halide perovskites possess great potential for electrochemical water splitting that has not been realized due to their intolerance to water. Here, methylammonium lead halide perovskites (MAPbX3 ) are used to electrocatalyze water oxidation in aqueous electrolytes by creating MAPbX3 @AlPO-5 host-guest composites. Due to the protective feature of the zeolite matrix, halide perovskite nanocrystals (NCs) confined in aluminophosphate AlPO-5 zeolites achieve an excellent stability in water. The resultant electrocatalyst undergoes dynamic surface restructuring during oxygen evolution reaction (OER) with the formation of an edge-sharing α-PbO2 active layer. The existence of charge-transfer interactions at the MAPbX3 /α-PbO2 interface significantly modulates the surface electron density of the α-PbO2 and optimizes the adsorption free energy of oxygen-containing intermediate species. Furthermore, the soft-lattice nature of halide perovskites enables more facile triggering of lattice-oxygen oxidation of nanostructured α-PbO2 , exhibiting pH-dependent OER activity and non-concerted proton-electron transfer for MAPbX3 @AlPO-5 composite. As a result, the developed MAPbBr3 @AlPO-5 composite manifests an ultralow overpotential of 233mV at 10 mA·cm-2 in 1M KOH. Our findings offer facile access to halide perovskite applied to water electrolysis with enhanced intrinsic activity, providing a new paradigm for designing high-efficiency OER electrocatalysts. This article is protected by copyright. All rights reserved.

Passivating Perovskites in Air Via an Alternating Cation Interlayer Phase Formed by Benzylamine Vapor Fumigation

Abstract2D perovskites are widely employed to improve efficiency and stability of perovskite solar cells (PSCs), but the processes are rarely accomplished in air due to the difficulty of controlling the formation processes. An ultra‐thin 2D capping layer with an alternating cation interlayer (ACI) structure is in situ formed by fumigating 3D perovskites with benzylamine vapor. The whole process is finished in air within 10 s regardless of the humidity, after which both defects and tensile strain are reduced and the interfacial energy band gets benignly aligned to a type‐I heterojunction, avoiding direct charge recombination at the interface. Theoretical analysis reveals that the ACI phase is thermodynamically more stable than an analogous Ruddlesden–Popper phase. The strategy can passivate various perovskites, including methylammonium (or multi‐cation) lead (or lead/tin mixed) halide perovskites, prepared via either vapor or solution approaches, increasing the absolute power conversion efficiency by up to 2.5%. It can uniformly passivate PSCs without area limitation, and provide a repeatable methodology for passivating perovskites.

Photocatalytic Properties of ZnO:Al/MAPbI3/Fe2O3 Heterostructure: First-Principles Calculations.

We report on theoretical investigations of a methylammonium lead halide perovskite system loaded with iron oxide and aluminum zinc oxide (ZnO:Al/MAPbI3/Fe2O3) as a potential photocatalyst. When excited with visible light, this heterostructure is demonstrated to achieve a high hydrogen production yield via a z-scheme photocatalysis mechanism. The Fe2O3: MAPbI3 heterojunction plays the role of an electron donor, favoring the hydrogen evolution reaction (HER), and the ZnO:Al compound acts as a shield against ions, preventing the surface degradation of MAPbI3 during the reaction, hence improving the charge transfer in the electrolyte. Moreover, our findings indicate that the ZnO:Al/MAPbI3 heterostructure effectively enhances electrons/holes separation and reduces their recombination, which drastically improves the photocatalytic activity. Based on our calculations, our heterostructure yields a high hydrogen production rate, estimated to be 265.05 μmol/g and 362.99 μmol/g, respectively, for a neutral pH and an acidic pH of 5. These theoretical yield values are very promising and provide interesting inputs for the development of stable halide perovskites known for their superlative photocatalytic properties.

Insight into the interface engineering between methylammonium lead halide perovskites and gallium oxide: a first-principles approach.

Interface engineering of the organo-lead halide perovskite devices has shown the potential to improve their efficiency and stability. In this study, the atomic, electronic, optical and transport characteristics of MAPbI3/Ga2O3 and MAPbCl3/Ga2O3 interfaces were investigated by using first-principles calculations. Eight different interfacial models were established and the interfacial properties were discussed. The results show that the PbI/O configuration exhibits the largest bonding strength out of all eight interfacial configurations. Owing to the larger interfacial interaction, the charge transfer at the PbI/O interface is significantly more than that at the other interfaces. The analysis of absorption spectra indicates that the Ga-terminated perovskite/Ga2O3 heterostructures are expected to have great potential for efficient optoelectronic applications. The analysis of transmission spectra shows that the MA/O configurations with more transmission peaks near the Fermi level exhibit lower resistance compared to others. The results of our study could help understand the interfacial engineering mechanism between perovskite and Ga2O3.

High-pressure investigations in CH3NH3PbX3 ( X = I, Br, and Cl): Suppression of ion migration and stabilization of low-temperature structure

Hybrid organic-inorganic halide perovskites represent a promising next-generation photovoltaic material with drawbacks for structure stability and composition concerns. Demonstrations of ion migration and molecular dynamics suggest room for structural contraction and subsequent property adjustments. Here, we deploy dielectric and infrared spectroscopy under external pressure to probe the full structural phase diagram and dielectric response of methylammonium lead halide perovskites ${\mathrm{CH}}_{3}{\mathrm{NH}}_{3}\mathrm{Pb}{X}_{3}$ ($X\phantom{\rule{4pt}{0ex}}=$ I, Br, or Cl). Ion migration can be fully suppressed by pressure beyond 4 GPa. The low-temperature orthorhombic phase transition can be gradually enhanced and stabilized at ambient conditions with increasing pressure. A slow relaxation mode, presumably the motion of the ${\mathrm{CH}}_{3}{\mathrm{NH}}_{3}^{+}$ cation, is observed at lower pressure and is absent in the orthorhombic phase for every halide.

Water-assistant ultrahigh fluorescence enhancement in perovskite polymer-encapsulated film for flexible X-ray scintillators

Methylammonium lead halide perovskites are well-known having a poor stability towards moisture. Water causes degradation of ionic perovskites and weaken the optical and electronic performance of perovskite-based devices. Main strategies to improve moisture stability are compositional engineering, surface engineering and matrix encapsulation. Herein, encapsulation strategy is implemented through screening a polymer matrix, a hydrophobic room-temperature vulcanized silicone rubber (RTV-2). Owing to the positive effect of moderate water on the performance of perovskites, the obtained MAPbBr3/RTV-2 composite film is processed with water post-treatment to undergo surface engineering. The composite film achieves a remarkable 8-fold fluorescence enhancement. Luminous efficiency of the film loaded on a 380 nm chip is improved from 51.4 lm/W to 135.37 lm/W. The flexible MAPbBr3/RTV-2 film responds sensitively under X-ray irradiation. Its detection limit is down to 12 nGyair s−1, 400 times lower than the regular dosage in X-ray diagnostics (5.5 μGy s−1). These results provide guidance to design perovskite-based devices with bright luminescence and excellent flexibility to qualify the wearable X-ray detectors for dose monitoring.

Ligand Coverage and Exciton Delocalization Control Chiral Imprinting in Perovskite Nanoplatelets

Chiral perovskites have recently generated significant interest, yet little is known about how their chiro-optical properties arise. In this study, chiral methylammonium lead halide perovskite nanoplatelets (NPLs) with varied halide and ligand compositions are prepared by using direct synthetic methods. Circular dichroism (CD) and 1H NMR studies find a nonlinear relationship between the chiroptical properties and the ratio of chiral phenylethylammonium (PEA) to achiral octylamine (OA) ligands on the NPL surface. We use density functional theory (DFT) computations and a chiral imprinted particle-in-a-box model to rationalize the experimentally observed CD spectra, and we find that the saturation of the induced chirality depends on the size of the perovskite exciton relative to the size of the ligand moleclues. Temperature-dependent CD and 1H NMR studies, combined with DFT analysis, show that both the CD intensity and sign depend strongly on the structure and orientation of the ligands. This work reveals the complex nature of chiral imprinting in perovskite nanostructures and establishes a simple physical model for ligand-induced chiral imprinting to guide the further development of chiral materials.

Ag nanowires assisted CH3NH3PbBr3–ZnO heterostructure with fast negative photoconductive response

Due to its attractive interaction with light, negative photoconductivity (NPC) has received widespread attention and has been used in optoelectronic logic devices with excellent performance. However, long negative response time triggered by photogenerated carriers trapping mechanism became a bottleneck in further application. Therefore, an enhanced strategy that can speed up negative response is urgently needed. Herein, we prepared a zinc oxide microwire (ZnO MW)–silver nanowires (Ag NWs)–methylammonium lead halide perovskite (CH3NH3PbBr3) heterostructure with enhanced negative response than the previous NPC device. The Ag NWs with high mobility at the interface of ZnO and CH3NH3PbBr3 accelerate the photoresponse time from 50 to 5.4 s and improve the dark current recovery time by two orders of magnitude. This work provides a strategy to improve the negative response speed with simple operation, which represents a step toward applications in the field of fast NPC optoelectronics.

Electrically Modulated Near-Infrared/Visible Light Dual-Mode Perovskite Photodetectors.

Dual-mode photodetectors (PDs) have attracted increasing interest owing to their potential optoelectrical applications. However, the widespread use of PDs is still limited by the high cost of epitaxial semiconductors. In contrast, the solution processability and wide spectral tunability of perovskites have led to the development of various inexpensive and high-performance optoelectronic devices. In this study, we develop a high-performance electronically modulated dual-mode PD with near-infrared (NIR) narrowband and visible light broadband detection based on organic-inorganic hybrid methylammonium lead halide perovskite (MAPbX3; MA = CH3NH3 and X = Cl, Br, and I) single crystals with a pnp configuration. The operating mode of the dual-mode PD can be switched according to voltage bias polarity because the photon absorption region and carrier transport performance are tuned at different bias voltages. The dual-mode PD exhibits a NIR light responsivity of 0.244 A/W and a narrow full width at half-maximum of ∼12 nm at 820 nm at positive voltages and an average visible light responsivity of ∼0.13 A/W at negative voltages. The detectivities of both modes are high (∼1012 Jones), and the linear dynamic range is wide (>100 dB). Our study provides a new method for fabricating multifunctional PDs and can expand their application in integrated imaging systems.

Fast Lead-Free Humidity Sensor Based on Hybrid Halide Perovskite

An environmentally friendly analog of the prominent methylammonium lead halide perovskite, methylammonium bismuth bromide (MA3Bi2Br9), was prepared and investigated in the form of powder, single crystals and nanowires. Complete characterization via synchrotron X-ray diffraction data showed that the bulk crystal does not incorporate water into the structure. At the same time, water is absorbed on the surface of the crystal, and this modification leads to the changes in the resistivity of the material, thus making MA3Bi2Br9 an excellent candidate for use as a humidity sensor. The novel sensor was prepared from powder-pressed pellets with attached carbon electrodes and was characterized by being able to detect relative humidity over the full range (0.7–96% RH) at ambient temperature. Compared to commercial and literature values, the response and recovery times are very fast (down to 1.5 s/1.5 s).

DFT study of electronic structure and mobility of pristine and fluorinated methylammonium lead halide perovskites (CH 3 NH 3 PbX 3 , X = I, Br, Cl)

We present the electronic structure and mobility of pristine and fluorinated methylammonium lead halide perovskites (CH3NH3PbX3, X = I, Br, Cl) using DFT calculations. We find that both CH3NH3PbX3 and CF3NH3PbX3 exhibit direct bandgaps (1.5-2.8 eV) which lies within the suitable bandgap regime for solar cell applications. The carrier mobilities of fluorinated MAPbX3 are much lower than pristine MAPbX3 indicating poor solar cell performance in spite of possible gain in stability due to enhanced hydrophobicity. The fluorination does not affect the chemical stability as is evident from the negative formation and cohesive energies, but an extremely high dipole moment (6.88 Debye) of CH 3 NH 3 + may severely affect the charge carrier pathways.

Enhanced resistive switching behavior of CH3NH3PbI3 based resistive random access memory by nickel doping

Excessive iodine vacancies (VIs) in the methylammonium lead halide perovskites (MAPbI3) based resistive random access memories (RRAMs) will cause resistive switching (RS) performance degradation. In this study, nickel ions are utilized to limit the excessive VIs in MAPbI3 film. Based on the analysis of X-ray diffraction and X-ray photoelectron spectroscopy, it can be found that the doped nickel ions partially replace lead ions, which can effectively improve lattice integrity and suppress generating of the PbI2 and Pb0 to limit excessive VIs. The RRAM devices based on MAPbI3 and Ni doped MAPbI3 films as the resistive switching layer are fabricated in air atmosphere. Compared with the MAPbI3 device, the Ni doped MAPbI3 device shows more remarkable RS performance. The ON/OFF ratio and endurance of the Ni doped MAPbI3 device has reached 103 and 300 cycles. Moreover, illumination in the forming stage can further improve the ON/OFF ratio and endurance of the Ni doped MAPbI3 device to 104 and 400 cycles. This work provides a new method for the optimization of organic−inorganic hybrid perovskite RRAM with high ON/OFF ratio and stable endurance.

The study of electronic and optical properties of perovskites CH3NH3PbCl3 and CH3NH3PbBr3 using first-principle

At present, Organic-inorganic hybrid methylammonium lead halide perovskites MAPbX3 (MA= CH3NH3; X = Cl, Br) have recently attract attention scientific researchers, as a promising candidate for photovoltaic and optoelectronic devices. We have studied the electronic structures and optical properties of perovskites CH3NH3PbBr3 and CH3NH3PbCl3, using density functional theory (DFT). These physical properties are calculated by CASTEP code, such as the band structures, total density of states (TDOS), absorption coefficient, refractive index and optical conductivity. The analysis of band gap shows that these two perovskites are semiconducting materials. Calculated absorption coefficient of CH3NH3PbBr3 and CH3NH3PbCl3 shows an absorption peak around 3.87 eV and 2.04 eV, respectively. The above results provide good agreement with experimental work for optoelectronic properties of CH3NH3PbBr3 and CH3NH3PbCl3 materials.

Numerical study of inorganic Cs2TiBr6 solar cells with a double hole transport layers

The proposed Cesium Titanium Bromide (Cs2TiBr6) has piqued curiosity as an absorber layer for the next-generation renewable energy. This is especially due to their important properties such as high stability and nontoxicity. Nevertheless, the performance of solar cells based on this double-perovskite is still lower than methylammonium lead halide perovskite solar cells, which limited their commercialization in the real world. Up till now, the highest efficiency of the experimentally constructed PSC has been 3.28%, where Cs2TiBr6 was utilized as an absorber layer and both inorganic (TiO2) and organic (P3HT, C60) as charge transport materials. . In this work, Numerical modeling tools were used to optimize the active layer with the novel architecture Au /P3HT/CuSbS2/ Cs2TiBr6/TiO2/FTO using solar cell capacitance simulator (SCAPS-1D). The results obtained using double hole transport layers provide a higher efficiency for Cs2TiBr6 perovskite solar cell compared with the conventional structure.

Investigation of emission behaviour of perovskite nanocrystals using nano to microspheres of TiO2

The encapsulation of MAPbBr3 perovskites nanocrystals into the pores of TiO2 microspheres (m-TiO2) remarkably enhances the stability and PLQY to 95%.

Proton Transfer‐Driven Modification of 3D Hybrid Perovskites to Form Oriented 2D Ruddlesden–Popper Phases

Herein, it is shown how a proton transfer process between the organic moiety in 3D methylammonium lead halide perovskite and the introduced aliphatic alkylamines provides the basis for a fabrication route toward hybrid 3D/2D perovskites and finally purely 2D Ruddlesden–Popper (RP) perovskite phases, predominantly the n = 1 phase. Five alkylamines with varying aliphatic chain lengths, such as butylamine, octylamine, dodecylamine, hexadecylamine, and octadecylamine as antisolvents in toluene, are used, which quickly protonate during the spin‐coating deposition of thin perovskite films. Formation of hydrogen bonds between protonated alkylamines and lead halide slabs leads to mixed 3D/2D hybrid perovskites, where the ratio between the 3D and 2D phases can be adjusted by the concentration of the alkylamine containing antisolvents. Longer‐chain aliphatic alkylamines (12 carbon atoms or greater) are most prone to slice 3D perovskite into layered perovskites with efficient green emission reaching up to 38% for their photoluminescence quantum yield in films. Above a certain concentration threshold, 3D perovskite can be completely modified into 2D RP perovskite phases with crystalline orientation parallel to the substrate. The introduced facile perovskite phase modification approach provides a convenient way toward different kinds of 2D RP metal halide perovskite films with attractive optical properties.