Inorganic Lead Research Articles

Photo-induced charge transfer in composition-tuned halide perovskite nanocrystals with quinone and its impact on conduction current

A facile interfacial charge transfer (CT) with a reduced inter-layer energy band regulates the charge transport mechanism in any optoelectronic device. The enhancement in semiconductor-based device performance often demands improved CT dynamics and collection of free carriers with reduced charge recombination. In this work, we present a detailed inspection of the photo-induced CT between inorganic lead halide perovskite nanocrystals (PNCs) with varied compositions and their consequence on the charge transport process. The superior CT rate in mixed halide CsPbBr2Cl PNCs with naphthoquinone (NPQ) is revealed when compared with the parent CsPbBr3 PNCs and its anion-exchanged counterpart CsPbCl3. The glimpses of hole transfer contribution along with electron transfer are detected for CsPbBr2Cl with superior CT efficiency. The enhanced conduction current after the insertion of NPQ into the PNCs with a reduced hysteresis suggests an improved charge transport in the fabricated device compared to the pristine PNCs. These findings can contribute to a better understanding of multiple ways of engineering optoelectronic devices to boost performance and efficiencies and the concurrent role of the CT process in the conduction mechanism.

Porphyrinic Metal–Organic Framework Quantum Dots for Stable n–i–p Perovskite Solar Cells

AbstractAs the power‐conversion efficiency (PCE) of organic–inorganic lead halide perovskite solar cells (PSCs) is approaching the theoretical maximum, the most crucial issue concerns long‐term ambient stability. Here, the application of PCN‐224 quantum dots (QDs) is reported, a typical Zr‐based porphyrinic metal–organic framework (MOF), to enhance the ambient stability of PSCs. PCN‐224 QDs with abundant Lewis‐base groups (e.g., CO, C−N, CN) contribute to high‐quality perovskite films with enlarged grain size and reduced defect density by interaction with under‐coordinated Pb2+. Meanwhile, PCN‐224 QDs enable the well‐matched energy level at the perovskite/hole transport layer (HTL) interface, thereby facilitating hole extraction and transport. More importantly, PCN‐224 QDs‐treated HTL can capture Li+ from bis(trifluoromethanesulfonyl)imide additive, leading to the reduced aggregation and less direct contact with moisture for hygroscopic Li‐TFSI. Moreover, PCN‐224 QDs mitigated Li+ ion migration into the perovskite layer, thus avoiding the formation of deleterious defects. The resultant devices yield a champion PCE of 22.51%, along with substantially improved durability, including humidity, thermal and light soaking stabilities. The findings provide a new approach toward efficient and stable PSCs by applying MOF QDs.

Low-threshold green and red random lasing emission in inorganic halide lead perovskite microcrystals with plasmonic and interferential enhancement

Herein, low-threshold green and red random lasing actions were investigated in inorganic caesium lead bromide (CsPbBr3) and caesium lead iodide (CsPbI3) perovskite microcrystals, which were grown using metal organic chemical vapor deposition. Sharp random lasing emission peaks were visible on the right side of the broad photoluminescence emission spectra. Interferential patterned sapphire substrates and novel metal nanoparticles were used to enhance the lasing emission intensity and reduce the lasing emission thresholds. Fast-decayed random lasing oscillation dynamics and backscattering angular distribution of light confirmed that the multi-scattering of light was important in the reduction of the threshold in thin films on patterned sapphire substrates. Plasmonic enhancement between gold or silver nanoparticles and the perovskite microcrystals contributed similarly to low threshold random lasing emission, which was verified using the simulation result from the finite difference time domain (FDTD) method. This work has a wide range of applications in sensing, speckle-free imaging, illumination, and medical diagnosis.

Monitoring of the content of heavy metals in sunflower seeds and its processing products in Ukraine for 2018–2021

The article presents the results of research conducted at the State Research Institute of Laboratory Diagnostics and Veterinary-Sanitary Examination from 2018 to 2021 regarding the content of trace elements and toxic elements in sunflower seeds and their products of domestic production. During the studied period, 62 samples of sunflower seeds, 345 samples of sunflower meal, 289 samples of sunflower cake, and 68 samples of halva were analyzed. The preparation of samples was carried out by acid decomposition in nitric acid using a laboratory microwave system with closed-type autoclaves. The content of Lead, Cadmium, and Arsenic was determined by the method of atomic absorption spectrometry with electrothermal atomization and background correction with the Zeiman effect. The content of copper and zinc was determined by atomic absorption spectrometry with flame atomization with deuterium background correction. Mercury content – by the direct method of atomic absorption spectrometry. In all studied samples, the content of copper varied between 1.21–42.9 mg/kg, the content of zinc 17.7–75.40 mg/kg, the content of lead 0.011–1.121 mg/kg, the content of arsenic 0.0035–0.004 mg/kg, Mercury 0.005–0.051 mg/kg. The results of studies of sunflower seeds and halva for cadmium content were in the range of 0.052–0.234 mg/kg and 0.080–0.271 mg/kg. According to the obtained results, it was established that cadmium content exceeded the maximum permissible level value in five sunflower seeds and in eighteen halva samples, which is 2.7 % and 20.2 % of the total amount of the studied material. During the study of the content of inorganic pollutants Lead, Arsenic, Zinc, and Copper in sunflower seeds and halva, no violations of the maximum permissible levels were found. Regarding the analysis of meal and sunflower cake for the content of Cadmium, Lead, Arsenic, Copper, and Zinc, no violations of the MDR were detected. The contamination of seeds and halva with cadmium exceeded the legally permissible levels by 1.1 to 2.1 times. These results confirm literature data on the ability of sunflowers to accumulate cadmium, particularly in seeds. The analysis of the work demonstrates the need for more thorough and systematic control of sunflower raw materials both at the growing stage and in the process of harvesting, drying, and processing at various stages of feed and final product production.

The Influence of a Fire at an Illegal Landfill in Southern Poland on the Formation of Toxic Compounds and Their Impact on the Natural Environment.

Landfill fires pose a real threat to the environment as they cause the migration of pollutants to the atmosphere and water sources. A greater risk is observed in the case of wild landfills, which do not have adequate isolation from the ground. The aim of this article is to present the results of studies on the toxicity of waste from a fire in a landfill in Trzebinia (southern Poland). Both soil and waste samples were investigated. The samples were analyzed using the GC-MS method and the leachates using ICP-OES. A total of 32 samples of incinerated waste and soil were collected. The organic compounds included naphthalene, fluorene, phenanthrene, anthracene, acenaphthene, acenaphthylene, fluoranthene, pyrene, benzo (c) phenanthrene, benzo (a) anthracene, chrysene, benzo (ghi) fluoranthene, benzo (b + k) fluoranthene, benzo (a) fluoranthene, benzo (c) fluoranthene, benzo (a) pyrene, benzo (e) pyrene, perylene, indeno[1,2,3-cd] pyrene, benzo (ghi) perylene, and dibenzo (a + h) anthracene. Among the inorganic parameters, sulfates, chlorides, arsenic, boron, cadmium, copper, lead, and zinc were taken into account. Phenanthrene reached values exceeding 33 mg/L. Fluoranthene dominated in most of the samples. Sulfates and chlorides were present in the samples in concentrations exceeding 400 and 50 mg/L, respectively. Compounds contained in burnt waste may have a negative impact on soil and water health safety. Therefore, it is important to conduct research and counteract the negative effects of waste fires.

Multi-omics provide mechanistic insight into the Pb-induced changes in tadpole fitness-related traits and environmental water quality

Water pollution from lead/Pb2+ poses a significant threat to aquatic ecosystems, and its repercussions on aquatic animals have received considerable attention. Although Pb2+ has been found to affect numerous aspects of animals, including individual fitness, metabolic status, and symbiotic microbiota, few studies have focused on the associations between Pb2+-induced variations in fitness, metabolome, symbiotic microbiome, and environmental parameters in the same system, limiting a comprehensive understanding of ecotoxicological mechanisms from a holistic perspective. Moreover, most ecotoxicological studies neglected the potential contributions of anions to the consequences generated by inorganic lead compounds. We investigated the effects of Pb(NO3)2 at environmentally relevant concentrations on the Rana omeimontis tadpoles and the water quality around them, using blank and NaNO3-treated groups as control. Results showed that Pb(NO3)2 not only induced a rise in water nitrite level, but exposure to this chemical also impaired tadpole fitness-related traits (e.g., growth and development). The impacts on tadpoles were most likely a combination of Pb2+ and NO3-. Tissue metabolomics revealed that Pb(NO3)2 exposure influenced animal substrate (i.e., carbohydrate, lipid, and amino acid) and prostaglandin metabolism. Pb(NO3)2 produced profound shifts in gut microbiota, with increased Proteobacteria impairing Firmicutes, resulting in higher aerobic and possibly pathogenic bacteria. NaNO3 also influenced tadpole metabolome and gut microbiome, in a manner different to that of Pb(NO3)2. The presence of NO3- seemed to counteract some changes caused by Pb2+, particularly on the microbiota. Piecewise structural equation model and correlation analyses demonstrated connections between tissue metabolome and gut microbiome, and the variations in tadpole phenotypic traits and water quality were linked to changes in tissue metabolome and gut microbiome. These findings emphasized the important roles of gut microbiome in mediating the effects of toxin on aquatic ecosystem. Moreover, it is suggested to consider the influences of anions in the risk assessment of heavy metal pollutions.

Synthesis of cesium lead halide perovskite/zinc oxide (CsPbX3/ZnO, X= Br, I) as heterostructure photocatalyst with improved activity for heavy metal degradation.

Inorganic perovskites have been recognized as highly potent materials for the display and medical industries due to their outstanding features. However, there haven’t been many reports on their implications as a photocatalyst for the removal of heavy metals. Photocatalysis has been regarded as a significant approach for the removal of pollutants because of its great sustainability, improved efficiency, and reduced energy consumption. Here, we applied inorganic cesium lead halides (Br and I) with zinc oxide heterostructure as a photocatalyst for the first time. The heterostructure has been synthesized by the traditional hot injection strategy and its photocatalytic activity was systematically investigated. Interestingly, the CsPbX3/ZnO heterostructure as a photocatalyst has a homogeneous geometry and possesses an excellent degradation efficiency of over 50% under xenon UV-Visible light. The CsPbX3/ZnO catalyst carries superior oxidation/reduction properties and ionic conductivity due to the synergistic photogenerated charge carrier and interaction between CsPbX3 and ZnO. The recycling experiment showed the good stability of the catalysts. These findings suggest that inorganic lead halide heterostructure has the potential to be used for heavy metal degradation and water pollution removal catalysts.

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

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

51.2: Invited Paper: The inorganic lead halide perovskite nanocrystals： the materials control and stability approach

51.2: <i>Invited Paper:</i> The inorganic lead halide perovskite nanocrystals： the materials control and stability approach

Single- and Multilayered Perovskite Thin Films for Photovoltaic Applications.

Organic–inorganic lead halide perovskites materials have emerged as an innovative candidate in the development of optoelectronic and photovoltaic devices, due to their appealing electrical and optical properties. Herein, mix halide single-layer (~95 nm) and multilayer (average layer ~87 nm) CH3NH3PbIBr2 thinfilms were grown by a one-step spin coating method. In this study, both films maintained their perovskite structure along with the appearance of a pseudo-cubic phase of (200) at 30.16°. Single-layer and multilayer CH3NH3PbIBr2 thinfilms displayed leaky ferroelectric behavior, and multilayered thinfilm showed a leakage current of ~5.06 × 10−6 A and resistivity of ~1.60 × 106 Ω.cm for the applied electric field of 50 kV/cm. However, optical analysis revealed that the absorption peak of multilayered perovskite is sharper than a single layer in the visible region rather than infrared (IR) and near-infrared region (NIR). The band gap of the thinfilms was measured by Tauc plot, giving the values of 2.07 eV and 1.81 eV for single-layer and multilayer thinfilms, respectively. The structural analysis has also been performed by Fourier transform infrared spectroscopy (FTIR). Moreover, the fabricated CH3NH3PbIBr2 as an absorber layer for photoelectric cell demonstrated a power conversion efficiency of 7.87% and fill factor of 72%. Reported electrical, optical and photoelectric efficiency-based results suggest that engineered samples are suitable candidates for utilization in optoelectronic and photovoltaic devices.

Effect of Dimensionality on Photoluminescence and Dielectric Properties of Imidazolium Lead Bromides.

Hybrid organic–inorganic lead halide perovskites have emerged as promising materials for various applications, including solar cells, light-emitting devices, dielectrics, and optical switches. In this work, we report the synthesis, crystal structures, and linear and nonlinear optical as well as dielectric properties of three imidazolium lead bromides, IMPbBr3, IM2PbBr4, and IM3PbBr5 (IM+ = imidazolium). We show that these compounds exhibit three distinct structure types. IMPbBr3 crystallizes in the 4H-hexagonal perovskite structure with face- and corner-shared PbBr6 octahedra (space group P63/mmc at 295 K), IM2PbBr4 adopts a one-dimensional (1D) double-chain structure with edge-shared octahedra (space group P1̅ at 295 K), while IM3PbBr5 crystallizes in the 1D single-chain structure with corner-shared PbBr6 octahedra (space group P1̅ at 295 K). All compounds exhibit two structural phase transitions, and the lowest temperature phases of IMPbBr3 and IM3PbBr5 are noncentrosymmetric (space groups Pna21 at 190 K and P1 at 100 K, respectively), as confirmed by measurements of second-harmonic generation (SHG) activity. X-ray diffraction and thermal and Raman studies demonstrate that the phase transitions feature an order–disorder mechanism. The only exception is the isostructural P1̅ to P1̅ phase transition at 141 K in IM2PbBr4, which is of a displacive type. Dielectric studies reveal that IMPbBr3 is a switchable dielectric material, whereas IM3PbBr5 is an improper ferroelectric. All compounds exhibit broadband, highly shifted Stokes emissions. Features of these emissions, i.e., band gap and excitonic absorption, are discussed in relation to the different structures of each composition.

Efficient Room‐Temperature Phosphorescence of 1D Organic–Inorganic Hybrid Metal Halides

Room‐temperature phosphorescence (RTP) has attracted considerable attention due to its potential applications in light‐emitting, bioimaging, and chemical sensing devices, but it is full of challenges to achieve new molecular systems for efficient RTP. Herein, three imidazole derivatives involving triplet excitons as organic cations are employed to synthesize three isostructural 1D lead halides with distinct emission characteristics, in which (2‐MBI)PbBr3 and (2‐PI)PbBr3 show the blue and broadband white fluorescence, respectively, while (5‐MBI)PbBr3 (5‐MBI = 5‐methylbenzimidazole) exhibits efficient green RTP peaking at 520 nm under UV excitation. The underlying photophysical regulatory mechanism is unveiled that extra‐molecular “heavy atomic effects” and the spin–orbit coupling from [PbBr3−]∞ units enhance the intersystem crossing and Dexter‐type electron transfer of excitons from inorganic units to triplet states (Tn) in 5‐MBI cations. An information encryption pattern is also realized by combining the different photoluminescence of these 1D organic and inorganic hybrid lead halides. This study suggests a feasible strategy to modulate the photoluminescence to achieve efficient RTP in low‐dimensional hybrid metal halides.

Optimization of the Anti-Solvent Method for the Fabrication of Cu Electrode-Based High-Efficiency Perovskite Solar Cell

Organic–inorganic lead halide perovskite is promising photovoltaic energy harvesting material to fabricate high-efficiency solar cells. To enhance the power conversion efficiency (PCE) and stability of the fabricated device, a high-quality, pinhole-free, and larger grain size perovskite film is essential. Anti-solvent-assisted crystallization is a popular technique to deposit perovskite thin film. With the help of this technique, perovskite layer can be deposited with smooth surface morphology, low surface defect density, and excellent carrier transport. However, choosing a proper anti-solvent is essential for highly efficient perovskite solar cells (PvSCs). Here, we qualitatively evaluate the impacts of different anti-solvent on methylammonium lead iodide (MAPbI <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ) perovskite film. We used chlorobenzene (CB), diethyl ether (Eth), toluene (TL), and isopropyl alcohol (IPA) as an anti-solvent. Our result demonstrates that the anti-solvent with a relatively higher boiling point and lower polarity contributes to superior efficiency, low hysteresis, and better reproducibility of MAPbI <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> active layer-based PvSCs. The device fabricated with CB anti-solvent exhibits the best PCE of 8.16% with a Cu-based electrode. This work provides a promising approach to controlling the growth and morphology of perovskite films and paves the way for further optimizing the fabrication process of large-area low-cost electrode-based high-efficiency devices.

Enhancement of UV-light harvesting in perovskite solar cells by internal down-conversion with Eu-complex hole transport layer

Recently, based on a lot of advantages of organic–inorganic lead halide perovskites, they have been applied in many ways, among which it exhibited outstanding characteristic for photovoltaic performance in application to solar cells. The CH3MH3PbI3 (MAPbI3)-perovskite solar cells (PSCs) show high solar energy conversion efficiency compared to conventional solar cells, but because they are greatly affected by external environments (such as temperature, moisture, light, etc.). For this reason, detailed researches are needed to improve the performances of the perovskite materials and prevent the degradation of the PSCs. Since less than 50% of sunlight contains the visible light and most of its energy can be used, the converting incident light from UV and IR regions into visible light for more productive and efficient solar cells must also be studied as well as the stability improvement. The main purpose of this study is to enhance the availability of UV-light used in the PSCs. Ultimately, we tried to increase the utilization of UV-light in sunlight and consequently improve the performance of the PSCs. Therefore, PSCs to be used were synthesized by controlling amounts of Eu-complex and injecting them into PEDOT:PSS to give a change in the hole transport layers (HTLs). By introducing Eu-complex, a down-conversion material, that absorbs light in UV range and re-emits the light in visible range into PEDOT:PSS, which has a great advantage as HTL with stability against UV-light and generation of more photon increase light-harvesting. As a result, the Eu-complex was shown to enhance the energy conversion efficiency of the PSCs as much as 25% and to raise the light-harvesting of the UV region through the internal down-conversion process.

Superfast desulfurization for protein chemical synthesis and modification

Superfast desulfurization for protein chemical synthesis and modification

Low‐Power‐Consumption, Reversible 3D Optical Storage Based on Selectively Laser‐Induced Photoluminescence Degradation in CsPbBr3 Quantum Dots Doped Glass

AbstractIn recent years, inorganic lead halide perovskite quantum dots have been used in various optoelectronic fields for their excellent luminescence properties, such as narrow emission bands, ultra‐wide tunable emission wavelength, and high quantum efficiency. In this paper, different from luminescence optimization in most research, luminescence degradation of perovskite quantum dots is addressed by femtosecond laser irradiation and successfully used for three‐dimensional data storage in CsPbBr3 quantum dots doped glass. Photoluminescence (PL) degradation can be finely modulated by adjusting the laser parameters. PL degradation mechanism, investigated by optical spectroscopy and morphology characterization, is attributed to laser‐induced decomposition, recrystallization, and defection of CsPbBr3 quantum dots. Laser‐induced PL degradation and the followed PL recovery by heat treatment are repeated for several cycles, showing good reversibility. Multilayer PL degradation patterns are written into the glass and read out without crosstalk, indicating high‐reliability 3D optical storage characteristics. Amazingly, PL degradation can be induced by just a low‐energy single laser pulse with estimated subpicosecond writing time per bit, demonstrating its potential in high‐speed, low‐power consumption 3D optical storage.

Fluorine-containing organic ammonium salt-doped inverted inorganic perovskite solar cells

Inorganic lead halide perovskites have a reasonable energy bandgap, which makes them ideal for tandem devices. As a result, inorganic lead halide perovskite solar cells (PSCs) could be prospective next-generation solar materials, but the issue of instability under moisture remains unaddressed. Adding 4-fluoro-phenyl-ethylammonium iodide (F-PEAI) spacer cations to the perovskite precursor solution is an elementary addition method to improve the performance of PSCs. We study the impact of F-PEAI on the perovskite crystal phase and the effect of F-PEAI concentration on PSC performance. F-PEAI was used to passivate interfacial flaws and vacancies in inverted inorganic PSCs and improve moisture tolerance, resulting in a mixed 2D/3D heterostructure. A small number of F-PEAI-treated PSCs have changed interfacial characteristics, resulting in better charge extraction and less charge recombination. The power conversion efficiency (PCE) of the F-PEAI treated device is much higher than that of the control group, and the PCE is improved to more than 11%. To attain high efficiency, all-inorganic perovskites can be modified using a straightforward method.

Bi and Sn Doping Improved the Structural, Optical and Photovoltaic Properties of MAPbI3-Based Perovskite Solar Cells

One of the most amazing photovoltaic technologies for the future is the organic–inorganic lead halide perovskite solar cell, which exhibits excellent power conversion efficiency (PCE) and can be produced using a straightforward solution technique. Toxic lead in perovskite can be replaced by non-toxic alkaline earth metal cations because they keep the charge balance in the material and some of them match the Goldschmidt rule’s tolerance factor. Therefore, thin films of MAPbI3, 1% Bi and 0%, 0.5%, 1% and 1.5% Sn co-doped MAPbI3 were deposited on FTO-glass substrates by sol-gel spin-coating technique. XRD confirmed the co-doping of Bi–Sn in MAPbI3. The 1% Bi and 1% Sn co-doped film had a large grain size. The optical properties were calculated by UV-Vis spectroscopy. The 1% Bi and 1% Sn co-doped film had small Eg, which make it a good material for perovskite solar cells. These films were made into perovskite solar cells. The pure MAPbI3 film-based solar cell had a current density (Jsc) of 9.71 MA-cm−2, its open-circuit voltage (Voc) was 1.18 V, its fill factor (FF) was 0.609 and its efficiency (η) was 6.98%. All of these parameters were improved by the co-doping of Bi–Sn. The cell made from a co-doped MAPbI3 film with 1% Bi and 1% Sn had a high efficiency (10.03%).

Influence of spin–orbit coupling and biaxial strain on the inorganic lead iodide perovskites, APbI3 (A = K, Rb, and Cs)

Recently, inorganic metal halide perovskites, APbI3 (A = K, Rb, and Cs), have attracted increased attention in the research community of photovoltaic technology due to their superior stability and exceptional structural, electronic, and optical properties. In this paper, the influence of biaxial compressive and tensile strains (−6% to +6%) on the optoelectronic properties of APbI3 perovskites is thoroughly investigated using density functional theory, based on first-principles calculations. Additionally, this study identifies the function of the A-cation in the optoelectronic properties of APbI3. We find that the biaxial strain in APbI3 can significantly increase its absorbance, both in the visible and ultraviolet light energy range. Interestingly, the absorption coefficient, dielectric function, and electron loss function are tuned into visible ranges when a compressive strain is applied, whereas these functions move into the ultraviolet region for tensile strain. Furthermore, the electronic band structure shows that the APbI3 compounds are all semiconductors with direct bandgap ranges of 0.92–1.09 eV and 1.9 eV at the R-point. The value of the bandgap decreases to 0.17, 0.25, and 0.32 eV for KPbI3, RbPbI3, and CsPbI3, respectively, when the spin–orbit coupling effect is considered. Moreover, the bandgap of APbI3 shows a decreasing trend and tends towards the metallic condition when compressive strain is applied. In addition, when tensile strain is increased, the bandgap of APbI3 exhibits an increasing trend. Therefore, based on the optical and electronic properties, applying a biaxial strain should make APbI3 compounds suitable for optoelectronic device applications.

Photoinduced large polaron transport and dynamics in organic–inorganic hybrid lead halide perovskite with terahertz probes

Organic-inorganic hybrid metal halide perovskites (MHPs) have attracted tremendous attention for optoelectronic applications. The long photocarrier lifetime and moderate carrier mobility have been proposed as results of the large polaron formation in MHPs. However, it is challenging to measure the effective mass and carrier scattering parameters of the photogenerated large polarons in the ultrafast carrier recombination dynamics. Here, we show, in a one-step spectroscopic method, that the optical-pump and terahertz-electromagnetic probe (OPTP) technique allows us to access the nature of interplay of photoexcited unbound charge carriers and optical phonons in polycrystalline CH3NH3PbI3 (MAPbI3) of about 10 μm grain size. Firstly, we demonstrate a direct spectral evidence of the large polarons in polycrystalline MAPbI3. Using the Drude–Smith–Lorentz model along with the Frӧhlich-type electron-phonon (e-ph) coupling, we determine the effective mass and scattering parameters of photogenerated polaronic carriers. We discover that the resulting moderate polaronic carrier mobility is mainly influenced by the enhanced carrier scattering, rather than the polaron mass enhancement. While, the formation of large polarons in MAPbI3 polycrystalline grains results in a long charge carrier lifetime at room temperature. Our results provide crucial information about the photo-physics of MAPbI3 and are indispensable for optoelectronic device development with better performance.