The organic–inorganic hybrid perovskite CH3NH3PbI3 is becoming an interesting material in the field of energy harvesting. This material is one of the cleanest and cheapest components in solar cells which is available in ample amounts. However, most of the previous research work was done on thin film of this material. In the present work we describe the preparation of a powder containing nanoparticles of CH3NH3PbI3 using a sonochemical method. Characterization of the product was done by various methods, such as HRTEM, FTIR, PL, DLS and XRD. The particles were found to be highly crystalline (tetragonal crystal structure), polygonal in shape and having diameters of 10–40 nm. 相似文献
Hybrid organic-inorganic perovskite materials have obtained considerable attention due to their exotic optoelectronic properties and extraordinarily high performance in photovoltaic devices. Herein, we successively converted the ultrathin PbI2/MoS2 into the CH3NH3PbI3/MoS2 heterostructures via CH3NH3I vapor processing. Atomic force microscopy (AFM)、Scanning electron microscopy (SEM) and X-ray photoemission spectroscopy (XPS) measurements prove the high-quality of the converted CH3NH3PbI3/MoS2. Both MoS2 and CH3NH3PbI3 related photoluminescence (PL) intensity quenching in CH3NH3PbI3/MoS2 implies a Type-II energy level alignment at the interface. Temperature-dependent PL measurements show that the emission peak position shifting trend of CH3NH3PbI3 is opposite to that of MoS2 (traditional semiconductors) due to the thermal expansion and electron-phonon coupling effects. The CH3NH3PbI3/TMDC heterostructures are useful in fabricating innovative devices for wider optoelectronic applications. 相似文献
Organic-inorganic hybrid CH3NH3PbI3 perovskite has a great potential for applications in low-cost photovoltaic devices. However, the doped and substitution of Pb sites in CH3NH3PbI3 has not been widely reported. In this article, a quantum mechanical model was applied to determine why all divalent cations cannot substitute the Pb cations of CH3NH3PbI3 perovskite. The evaluation was performed by comparison the model with experimental results. On this basis, we carefully examined 42 types of cations and identified only nine kinds of cations including Ca2+, Sr2+, Sc2+, Ti2+, V2+, Y2+, Zr2+, Nb2+ and Sn2+ for doped into Pb sites. In these cases, it is expected that the corresponding compound would be single phase. Finally, an analysis was performed based on first principle, and the results indicate that divalent cations substituting the Pb sites modify the band structure and influence the performance of perovskite-based photostatics. 相似文献
Spin coated perovskite thin films are known to have an issue of pinholes & poor morphology control which lead to poor device-to-device repeatability, that is an impediment to scale-up. In this work, Methylamine vapor annealing process is demonstrated which consistently leads to high-quality perovskite thin-films with an average grain-size of 10–15 μm. The improvement in film morphology enables improvement in effective carrier recombination lifetime, from 21 μs in as-deposited films to 54 μs in vapor-annealed films. The annealed films with large-grains are also more stable in ambient conditions. Devices made on annealed perovskite films are very consistent, with a standard deviation of only 0.7%. Methylamine vapor annealing process is a promising method of depositing large-grain CH3NH3PbI3 films with high recombination lifetime and the devices with improved performance. 相似文献
Band gap modulation engineering is an important step in the application of optoelectronic materials. In this paper, the first-principles calculations were carried out to study the influence of strain, external electric field, spatial orientation of organic cation on the band gaps and electronic structures of organic-inorganic hybrid halide perovskites CH3NH3PbI3. The results show that both the uniform strain and the tetragonal deformation can modulate the band gap obviously. The electric field of 0.2 V/Å is the critical point of the band gap modulation. The band gap increases when an electric field is applied from 0 to 0.2 V/Å. The electric field above 0.2 V/Å will cause the band gap to decrease. The spatial orientation of the organic cation also has modulation influence on the band gap of CH3NH3PbI3, but has no effect on the direct semiconductor characteristics. The above results will be helpful to study the band gap modulation of other organic-inorganic hybrid halide perovskites. 相似文献
Large-grain-size and void-free CH3NH3PbI3 films with bilayer structure are fabricated by spin-coating a PbI2 layer onto a mesoporous TiO2 layer and sequentially spraying CH3NH3I (methylammonium iodide, MAI) multilayers. The sprayer is controlled by a homemade three-axis computer numerical control machine; thus, the substrates are coated by successive parallel passes achieved by moving the nozzle. Spray deposition at the optimal spray rate and substrate temperature produces a large-grain-size and void-free methylammonium lead iodide (MAPbI3) bilayer structure. The mesoporous TiO2 layer plays an important role in electron transport by preventing the return of electrons to the perovskite layer and decreasing the contact resistance at the perovskite/compact TiO2/fluorine tin oxide interface. When the films are incorporated into a solar cell device with a conductive carbon counter electrode, a maximum power conversion efficiency of 10.58% is realised. 相似文献
Perovskite CH3NH3PbI3 (MAPbI3) single crystal was grown using inverse temperature crystallization method. Crystallinity of the perovskite was confirmed by X-ray diffraction. Photoluminescence (PL) spectra revealed abnormal behavior due to a temperature-induced orthorhombic to the tetragonal phase transition. Four PL emission peaks, A, B, C, and D, were observed in the low temperature regime. Peaks A and B were observed at 756 and 776?nm?at 12?K, and were blue-shifted and disappeared at 130 and 70?K, respectively. Peaks C and D were observed at 789 and 807?nm?at 40?K and were also blue-shifted to 780 and 794?nm?at 100?K. On the other hand, the peak C red-shifted to 799?nm from 100 to 140?K because of an orthorhombic to the tetragonal phase change and was also blue-shifted above 140?K. From the excitation intensity- and temperature-dependent PL results, peaks A and B were assigned to the free-exciton and bound-exciton of the orthorhombic phase crystal, respectively. In addition, peaks C and D were associated with the free-exciton and bound-exciton of the tetragonal phase crystal, respectively. The activation energy of peak C was calculated to be 98?meV from temperature dependence of the PL intensity. 相似文献
In this work, a new idea of organic-inorganic hybridization was proposed to fabricate flexible p-type - Sb2Te3/CH3NH3I thin films. The CH3NH3I has a strong adsorption which can promote the growth of organic molecules, improve the crystallization, and finally increase electrical conductivity. Post-annealing of the fabricated films increased the phonon scattering, thus resulting in a reduction of thermal conductivity and an increased ZT value. The annealed hybrid-composite film showed a significant enhancement in thermoelectric performance, with a maximum ZT value of 0.94 at a temperature of 413 K, which is twice as large as that of the as-deposited film. 相似文献
In this study, we built a perovskite solar cells(PSCs) model with a Au/CuSCN/CH3NH3Sn1−xPbxI3/TiO2/FTO glass structure using the SCAPS program and use polynomial fitting to obtain the relationship between the conduction/valence bands of CH3NH3Sn1−xPbxI3 and the x value, which is more complex and accurate than that in any previous research. The influences of thickness, electron and hole mobilities, relative permittivity, effective conduction band density, effective valence band density, and the value of x on the solar cell performance are analyzed. Furthermore, we simulate the situation where the doping concentration changes with the absorption layer depth of the device and a special bandgap is formed. The power conversion efficiency of the device improves from 19.96% to 20.52%, with an open-circuit voltage of 0.776 V, a short-circuit current of 33.79 mA/cm2, and a filling factor of 77.39% when double gradient doping is performed. The application value of gradient doping in the device absorption layer is obtained. 相似文献
The excitons in the orthorhombic phase of the perovskite CH3NH3PbI3 are studied using the effective mass approximation. The electron–hole interaction is screened by a distance‐dependent dielectric function, as described by the Haken potential or the Pollmann–Büttner potential. The energy spectrum and the eigenfunctions are calculated for both cases. The results show that the Pollmann–Büttner model, using the corresponding parameters obtained from ab initio calculations, provides better agreement with the experimental results.
Potassium tantalate niobate (KTa0.4Nb0.6O3, KTN) nanoparticles of perovskite structure were successsfully synthesized by a solvothermal method. The KTN nanoparticles
synthesized at 250 °C for 8 h with 1 to 4 M KOH concentration using isopropyl alcohol [(CH3)2 CHOH] as the solvent was composed of a single phase of cubic perovskite structure. Futhermore, the KTN powers synthesized
at the same conditions besides of using (CH3)2CHOH/H2O as a solvent compose of a single phase of tetragonal perovskite structure. The nanoparticles exhibit a mixture of cubic
and prism-like shapes with lengths of 100 nm to 500 nm and average cross sections of 200×200 nm2. The solvent dependence of the powder formation is discussed. X-ray diffraction and electron diffraction results show that
the powders have the needed tetragonal perovskite structure. The band gap of KTN nanoparticles is determined to be 3.26 eV
from the optical absorption spectra.
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In this study, a novel and facile route was utilized to synthesize methylammonium lead iodide (MAPbI3) perovskite microplate arrays with uniform morphology and predefined locations. Initially, large-area single-crystalline lead iodide (PbI2) thin sheets were synthesized through a solvent evaporation crystallization method for synthesizing PbI2 thin sheets. These PbI2 sheets were then employed as a seed layer to grow uniaxially aligned arrays of PbI2 microplates through lithographically defined microscale windows in a polymeric film. Thereafter, the PbI2 microplates were further intercalated with methylammonium iodide (MAI) to produce perovskite crystals. Structural and optical characterizations showed that the synthesized materials have a distinct heterojunction structures consisting of MAPbI3 perovskite microplates arrays and the underlying PbI2 thin sheet layer. The two-step process reported herein, which involves the uniaxial growth of PbI2 microplates and their conversion to MAPbI3 perovskite microplates with little dimensional change offers a new pathway for the fabrication of materials for integrated electronic and optoelectronic systems. 相似文献
Organohalide perovskite optoelectronics based upon large (mm‐sized) single crystals present exciting opportunities for new device platforms and fundamental studies. Herein, we report CH3NH3PbBr3 and CH3NH3PbI3 single crystals prepared via an inverse temperature crystallization method with strong near infrared photoresponses significantly below the optical gap. Light intensity dependent photocurrent measurements reveal the photoresponse is not a two‐photon phenomenon, but rather is derived from a linear mechanism. The effect (including responsivity and speed) is enhanced in a photoresistor architecture, indicating that the photoresponse is due to absorption into surface trap states in the crystal. Without any optimisation, respectable NIR responsivities at room temperature of ∼10‐2 A W−1 at a low 1V bias operating voltage are achieved. These results again demonstrate the remarkable potential of organohalide perovskites as light sensing materials, and the possibilities for engineering a new class of single crystal‐based optoelectronics.