As-prepared Perovskite Research Articles

Vertically Oriented 2D Perovskite Layer with n = 1 Phase Enables Efficient and Stable Inverted Perovskite Solar Cells.

Surface passivation with 2D perovskites has been reported to be important for high-performance perovskite solar cells (PSCs). However, it is challenging to achieve a controlled growth of 2D perovskites, which typically feature random orientation and various n number. In this paper, we fabricate a 2D layer with a highly ordered orientation and pure n = 1 phase on top of the perovskite film using the organic spacer molecule 7-fluoro-1,2,3,4-tetrahydroisoquinolinehydrochloride (7-FTH). The formed 2D perovskites feature a highly ordered orientation normal to the substrate and a pure n = 1 phase, which efficiently passivates surface defects of the as-prepared perovskite films and improves the energy level alignment between the perovskite film and electron transport layer. Consequently, the modified PSCs achieve a champion power conversion efficiency (PCE) of 24.65% with improved VOC and fill factor. After being stored in an N2 glovebox for 1200 h and kept in ambient air (room temperature and relative humidity of 50-70%) for 840 h, the modified devices retain 93% and 95% of its initial PCE, respectively.

Enhancement of orange emission in terbium-doped lead-free halide perovskite for flexible functional fibers and light-emitting diodes

In recent years, all-inorganic perovskites have attracted considerable research attention. However, the advancement of lead-based perovskites has encountered substantial challenges, redirecting current research efforts toward lead-free alternatives. In this study, we synthesized novel Cs4MnBi2Cl12 perovskite crystals at 80 °C. Furthermore, Tb3+ ions were introduced to enhance the fluorescence properties and stability of the as-prepared perovskite crystals (PCs). The photoluminescence quantum yield (PLQY) of Tb3+-doped PCs was 25.45 % (∼598 nm), making a two-fold increase compared with the original PCs. In the PCs, [BiCl6]3− octahedrons serve as energy collectors, generating excitons, while [MnCl6]4− octahedrons function as luminescence centers of the receptor. Owing to their entirely inorganic composition, the PCs exhibited exceptional stability under sunlight and across a wide range of temperatures. Finally, we applied the PCs to fiber composite paper and an light-emitting diode (LED) device, which retained their specific stability after the modification. The findings of this study offer nover insight for incorporating perovskites into fiber applications and optoelectronic devices.

Insights into structural, electronic, optical properties, and impedance spectroscopy of semi-doped perovskite Nd0.5Ba0.5CoO3: A theoretical and experimental study

In this study, the electronic, structural, and optical properties of semi-doped perovskite Nd0.5Ba0.5CoO3 (NBCO) were investigate using the CASTEP software, which relies on density functional theory (DFT) along with the correlation function of generalized gradient approximation (GGA) and Perdew-Burke-Ernzerhof (PBE). The mesh parameters of the (super) cell indicate that NBCO adopts an orthorhombic structure in the Pmmm space group, featuring a Coulomb Energy (EC) of approximately −244 eV. DFT and total density of states (DOS) analyses reveal that the as-prepared perovskite manifests metallic characteristics, and a notable covalent interaction is observed between the O-p and Co-d spin states, indicating strong hybridization between these orbitals. Remarkably, NBCO demonstrates 100 % spin polarization (P) at the Fermi level, with a calculated total magnetic moment of approximately 3.44 μB. Moreover, low dielectric loss (tgδ) values suggest facile electron movement, and impedance spectroscopy illustrates a dielectric relaxation phenomenon. DFT calculations predict an orthorhombic crystal structure with higher electron density at cobalt atom positions. Band structure and DOS analyses affirm metallic behavior owing to the robust hybridization between oxygen-p and cobalt-d orbitals. Optical property assessments reveal potential applications in spintronics and optoelectronics, with notable absorption in the ultraviolet–visible range. The conductivity spectra from impedance spectroscopy contribute to understanding temperature-dependent charge transport mechanisms. Dielectric constants decrease with increasing frequency and temperature, while dielectric losses remain low, indicating efficient electron movement. The material adheres to a metallic conduction mechanism as described by Drude's law, and the material's 100 % spin polarization at the Fermi level and a total magnetic moment of 3.44 μB are significant findings. Negative dielectric constants observed at specific frequencies suggest potential applications in metamaterials. Overall, the determined properties position NBCO cobaltite as a promising candidate for high-frequency devices, spintronic components, and sensors.

Effect of solvent annealing in the growth of MAPbI3 for perovskite solar cells

Perovskite solar cell (PSC) is recognized as one of the most promising solar cells because of a drastic enhancement in photovoltaic performance. Numerous studies showed that grain size in a perovskite layer plays a vital role in determining the PSC performance. It is expected that the large-sized grains are beneficial for PSCs due to less grain boundaries and reduced non-radiative recombination losses. The perovskite grains can be enlarged by many methods including solvent annealing approach in which an as-prepared perovskite film is annealed under dimethylformamide (DMF) vapor environment. In this work, the effect of the amount of DMF and annealing time on the surface morphology and photovoltaic parameters of PSCs were investigated and compared to the pristine devices. It was found from the inspection with FESEM images that perovskite grains were significantly enlarged as DMF was introduced. As a result, the overall photovoltaic parameters of DMF-based devices are superior to that of the pristine devices. The best device obtained using two rounds of 50 µL DMF for 15 minutes annealing shows maximum power conversion efficiency of 18.0% compared to 15.3% of the pristine devices.

Effects of ethylammonium and rubidium addition to guanidinium-based CH3NH3PbI3 perovskite photovoltaic devices prepared at 190 °C in ambient air

Effects of the addition of rubidium (Rb) and ethylammonium (CH3CH2NH3, EA) to guanidinium [C(NH2)3, GA]-based CH3NH3PbI3 perovskite solar cells were investigated. Lattice constants and the (100)-orientation of EA- and Rb-modified perovskite crystals increased compared with those of as-prepared perovskite. Abnormal increases of lattice constants of the GA- and EA-modified perovskite crystals prepared at 190 °C for 10 min in ambient air were also observed during the room temperature aging, which was due to crystal growth of the perovskites, and these features contributed to increased conversion efficiencies of devices based on the modified perovskites. Addition of GA and EA also effectively improved the photovoltaic properties of the device under indoor light conditions using white light-emitting diodes. First-principles calculations of the density of states and band structures indicated a reduction of the total energy through the addition of Rb or EA, suggesting that the current density was improved by the reduced band gap.

HPMC-Mediated ZnCl2 Doping Possible Substitution of Pb2+ for Environment-Friendly Halide Perovskite Solar Cell Fabrication

Research on halide perovskite solar cells is a rapidly evolving and active area of study within the field of photovoltaics. Replacement of lead from halide perovskite solar cells is a prerequisite due to its toxicity. In this research, an efficient and low surface defect of Zn2+ incorporated hybrid perovskite material was demonstrated, where Pb2+ is partially substituted with transitional metal Zinc. Herein, we report the incorporation of dopant material ZnCl2 with synthetic cellulose HPMC (Hydroxy propyl methyl cellulose) as a dopant to improve the surface morphology, crystallinity, and partial substitution of Pb2+ with Zn2+. Samples were prepared with different composition of ZnCl2 doping assisted with HPMC in MAPbI3 (methylammonium lead triiodide) for perovskite layer preparation. A device assembly of layer-by-layer architecture constituting FTO/TiO2(ETL)/MAPbI3/CuSCN(HTL) was fabricated for the experimental analysis. The as-prepared perovskite samples were characterized using different analytical tools to investigate optical absorption property, crystalline structure, functional group interaction, and surface morphology, respectively. Finally, the electrical performance of the perovskite solar cells was tested under AM 1.5 G solar illumination, and the data affirms that 10 wt% ZnCl2 doping assisted with HPMC media exhibits optimum performance with improved film quality.

Study of charge-transfer and energy-transfer properties of methylammonium-based-Pb-halide perovskites

The efficiencies of organic-inorganic halide perovskites have shown subjective increment in recent years, but the instability issues encumber their further development and applications. This article includes the synthesis of MAPbI3, MAPbICl2, and MAPbIClBr perovskites by one-step and two-step spin-coating methods. Further, we investigated the structural and optoelectronic properties of as-prepared perovskites and degraded perovskites after the degradation period (i.e., exposure to light, temperature, and humidity) of 30 days. Here, we also determined the structural & optoelectronic properties of as-prepared and degraded halide perovskite nanocrystals passivated by N, N-DMF and also studied their charge transfer & energy transfer characteristics by dissolving in MEH-PPV (poly(2-methoxy-5(2-ethylhexyloxy-1,4-phenylenevinylene)) polymer. Moreover, as-prepared MAPbI3 perovskite exhibits effective photoluminescence quenching evident from the highest stern-Volmer quenching constant (Ksv), enhancing charge-transfer efficiency in as-prepared MAPbI3:MEH-PPV composites. On the other hand, the energy-transfer process dominates between the host-polymer donor and guest perovskite as an acceptor due to the low PL quenching in degraded MAPbI3:MEH-PPV composites. However, as reported earlier, the stability of perovskite for LEDs is a challenging task. Still, in this manuscript, we stated that an inferior perovskite material for photovoltaics would prove to be a good perovskite material for LEDs applications.

Enabling extraordinary oxygen reduction reaction activity of dual alkaline earth-substituted perovskite cathodes for intermediate-temperature solid oxide fuel cells

Dual alkaline earth-substituted Pr0.94Ba1–2xSrxCaxCo2O5+δ perovskites are evaluated as potential cathodes for intermediate-temperature solid oxide fuel cells. When incorporating Sr2+ and Ca2+ into the lattice, the phase transformation from tetragonal layered perovskite to simple cubic perovskite can be identified. Benefitting from enhanced electrical conductivity, oxygen surface exchange and ionic diffusion rates, the as-prepared perovskite catalysts demonstrate highly electrocatalytic activity for oxygen reduction reaction. The Pr0.94Ba0.6Sr0.2Ca0.2Co2O5+δ cathode exhibits an area-specific resistance of 0.025 Ω cm2 at 700 °C, approximately decreased by = 60% relative to the pristine Pr0.94BaCo2O5+δ. It is discovered that Sr2+ and Ca2+ co-substituting lowers the charge transfer energy, as well as oxygen adsorption energy. Furthermore, the Pr0.94Ba0.6Sr0.2Ca0.2Co2O5+δ cathode-based fuel cell delivers a peak power density of 1194 mW cm−2 at 700 °C, along with outstanding short-term stability over a period of 160 h. Our results highlight a strategy of dual alkaline earth substitution for rationally designing the perovskite electrocatalysts.

Effect of Sr doping on structural, magnetic and transport properties of La1-ySryMn0.5Co0·5O3±δ

Structural, magnetic and magneto transport properties of La1-ySryMn0.5Co0·5O3±δ perovskites prepared by aqueous solution combustion synthesis were studied in detail. The effect of Sr doping on the properties of these perovskites was investigated. As-prepared perovskites were characterized using X-ray diffraction for single phase formation. Magnetic study was carried out for in depth analysis of the magnetic properties. AC susceptibility study shows a change in the behavior of undoped and doped compounds in low temperature region. Ferromagnetic interactions was found to increase in the low temperature region in the doped compounds compared to that in the undoped compound. The measurements on resistivity showed reduction with Sr doping up to y = 0.5. This is attributed to the high spin stabilized Co3+ ions which enhance the ferromagnetic interactions and the hopping probability of eg charge carriers.

Influence of Two- and Three-Dimensional Engineering on the Trap State Distribution and Photophysical Properties of Lead Halide Perovskite Polycrystals

Constructing a two- and three-dimensional (2D/3D) heterojunction structure on the surface of a 3D perovskite film, termed 2D/3D engineering, is effective in elevating the stability of perovskite polycrystal-based photovoltaic and photoelectronic devices; however, it remains controversial whether this protocol is favorable or detrimental to the device performance. Here, we prepare a series of 2D/3D perovskite films by post-treating the perovskite polycrystalline film with different concentrations of phenethylammonium iodide (PEAI). Systematic spectroscopy and electrochemical studies illustrate that PEAI can penetrate the 3D perovskite network and eliminate the intrinsic trap states of perovskite polycrystals, while the 2D perovskite nanosheets enriched on the top of the polycrystalline film may introduce additional trap states, which manipulate the photoluminescence performance and dynamics of the as-prepared perovskite films in an opposite manner. Based on this finding, the strategy of optimizing the photophysical properties of the host 3D perovskite through 2D/3D engineering is elaborated, paving the way for fabricating high-performance and high-stability perovskite polycrystalline films.

Improvement in Efficiency and Reproducibility for FAPbI3 Solar Cells with Rapid Crystallization

Clarifying the crystallization process of the perovskite FAPbI3 film is quite an important pathway for improving the performance of perovskite solar cells, and the annealing time is a key factor to control the nucleation and crystal growth. However, the existing electrodeposition method lacks systematic studies on the growth of the perovskite FAPbI3 film. Herein, we manipulate the annealing time precisely for growing a pure α-FAPbI3 perovskite film in the electrodeposition-assisted method. The perovskite pure α-FAPbI3 film can be synthesized by fast annealing in only 1 min, and the as-prepared perovskite film shows high solar light absorption capacity and large grains. Thus, the corresponding solar cells based on α-FAPbI3 show the best power conversion efficiency (PCE) of 13.33%, which is 32% higher than that of FAPbI3 solar cells annealed for a long time (20 min). More importantly, all of these PCE variances do not exceed 1% under different annealing times, indicating the high reproducibility of the perovskite solar cells based on this rapid crystallization method. With a phenethylammonium iodide passivation layer, the PCE can even be improved to 14.02%.

Syngas production and gas-N evolution over heterogeneously doped La-Fe-O perovskite-type oxygen carriers in chemical looping gasification of microalgae

Chemical looping gasification (CLG) is a promising technology for syngas production with low pollutant emission. In this study, doped La-Fe-O perovskites including LaFeO3 (LF), LaFe0.5Ni0.5O3 (LN5F5) and La0.3Ba0.7FeO3 (L3B7F) were developed for microalgae CLG. The as-prepared perovskites exhibited an outstanding performance in syngas production with accumulative syngas yield > 33 mol/kg. For gas-N evolution, perovskites were beneficial to the formation of NH3 and HCN, while the iron ore may convert precursors to NO. Below 400 °C, NOx can be stored on the perovskite surface in the form of nitrite/nitrate species. When the temperature was above 700 °C, NOx can be selectively reduced by reducing components in tar or syngas under the catalysis of L3B7F, resulting in the final reduction of NOx emission. Thus, CLG over L3B7F may be a promising way for efficient utilization of microalgae to overcome the intractable nitrogen-related obstacles in the commercial application of biomass gasification technologies.

Octahedral Distortion Co-Regulation via Dual Strategies toward Luminescence Enhancement for the MA4InBr7 Perovskite Single Crystal.

A series of novel perovskite single crystals are innovatively grown. Aiming to enhance the luminescence performance, octahedral distortion co-regulation via dual strategies for the as-prepared perovskite single crystals is performed. The distortion of the octahedral structure strengthens the electron-phonon coupling and electron localization, resulting in a more stable self-trapped state, which thereby increases the potential for radiative recombination, accompanied by the self-trapped exciton emission. Accordingly, the luminescence spectra of the as-prepared MA4In0.975Sb0.025Br7 single crystal can cover the 450-800 nm range, and the photoluminescence quantum yield is up to 81.25%.

Synthesis and photoluminescence properties of perovskite-structure Ba0.5Sr0.5TiO3: Sm3+ phosphors

Abstract Rare-earth ions doped luminescent materials have excellent optical properties and low energy consumption, which are widely used in optoelectronic devices. In this work, Sm3+-doped Ba0.5Sr0.5TiO3 perovskite phosphors were prepared by a convenient high-temperature solid-reaction method. A strong orange-red luminescence appeared at 600 nm, corresponding to the energy-level transition of 6H5/2 → 4F7/2. The optimal concentration of Ba0.5Sr0.5−x TiO3: xSm3+ was determined to be around x = 0.08. The forbidden band width and the fluorescence lifetime of Ba0.5Sr0.5TiO3: Sm3+ are 3.15 eV and 2.7 μs, respectively. The CIE coordinates are (0.509, 0.476). The as-prepared orange-red perovskite phosphors are expected to be used in white light–emitting diode (LED) devices.

Evaluation of three-dimensionally ordered macroporous LaFe1−xCoxO3 perovskites and their performance for catalytic oxidation of methane

Nowadays, excess methane emissions have caused serious environmental problems, of which catalytic oxidation is a practical and economically feasible technique for its decomposition and harm reduction. Here, three‐dimensionally ordered macroporous (3DOM) LaFe1−xCoxO3 (x = 0, 0.1, 0.3, 0.5) were prepared by colloidal crystal template (CCT) method using polynomial methacrylate (PMMA) as templates in order to evaluate their catalytic activities for methane. Numerous analytical techniques were used to characterize the physicochemical properties of as-prepared perovskite catalysts. The results showed that the morphology of the catalysts depended strongly on the PMMA template and an appropriate calcination temperature was decisive for the formation of a high-quality 3DOM structure, which affected the textural parameters, the surface compositions of the catalysts and further determined their catalytic activities for methane. Along with the doping of Co for Fe at the B site, the BET surface areas and crystallite sizes could be optimized, and the ratios of Fe4+/Fe3+, absorbed oxygen (Oads)/lattice oxygen (Olat) both increased with the increment of Co substitution, which were beneficial to improve the catalytic activity on CH4. However, the surface carbonate or hydroxide compounds also increased with the increment of Co doping and did harm to the catalytic activity in an opposite way. The final result was that the 3DOM LaFeO3 calcined at 700 ℃ (Ea = 70.9 kJ/mol, T50% = 548 ℃, T90% = 652 ℃), with the optimal pore size, pore volume, Fe4+/Fe3+ ratio, H2-TPR reducibility, on stream testing stability and carbon deposition resistance in low temperature, showed much better performance than the Co-doped 3DOM LaFe1−xCoxO3 (x = 0.1, 0.3, 0.5) in the methane catalytic process. However, it was also predictable that the performance of methane oxidation by Co-doped perovskites can be improved if the surface carbonate or hydroxide compounds can be effectively controlled in the future by surface engineering methods like acid treated or others to eliminate La segregation on its surface.

Room temperature crystallization and stability of halide perovskite thin films

<p indent="0mm">The preparation of metal halide perovskite films with high crystallinity and high stability without heating in air is difficult to be realized, which is important for future large-scale applications of flexible perovskite solar cells. In this paper, we propose a method to realize the crystallization of perovskite thin films at room temperature, by using a mixed solution of three low-boiling polar molecules, 1,2-dimethoxyethane (DME), methylamine (MA), and ethanol (EA). The mixed solution effectively dissolves the perovskite precursor, and high crystallinity perovskite thin films can be prepared without annealing in air. The as-prepared perovskite film still maintains the lattice structure after 120 h of continuous illumination in air, showing high stability under water, oxygen, and illumination conditions. This method is suitable for the preparation of perovskite thin films with a band gap of <sc>1.60–1.78 eV.</sc> Finally, the flexible perovskite solar cells fabricated by this method achieved the highest photoelectric conversion efficiency of 19.63%. This provides a feasible direction for the large-scale commercial production of flexible perovskite solar cells.

Anion effect on properties of Zn-doped CH3NH3PbI3 based perovskite solar cells

High-quality perovskite films are crucial for developing efficient planar perovskite solar cells (PSCs). As-prepared perovskite films have low crystallinity and high level of trap densities, resulting in the deterioration of PSCs performances. Herein, a facile approach is adopted to fabricate high-quality CH 3 NH 3 PbI 3 films by incorporating different types of zinc salt, including zinc iodide (ZnI 2 ), zinc chloride (ZnCl 2 ), and zinc acetate (Zn(Ac) 2 ). It is demonstrated that zinc ions (Zn 2+ ) substitute a part of the lead ion (Pb 2+ ) sites, enlarging the grain size, and suppressing the formation of metallic lead. Moreover, the acetate anion bearing the carbonyl species (C O) effectively passivates the under-coordinated Pb 2+ defects and further reduces the defect densities at both the grain boundaries and interfaces. As a result, the planar PSCs with the Zn(Ac) 2 additive yield a champion power conversion efficiency (PCE) of 19.32%, which is 15% higher than that of the control device. Simultaneously, the outperforming device delivers remarkable stability, retaining 87% of its original efficiency after aging for 500 h under ambient conditions. • Enhanced Gibbs free energy of nucleation induced by zinc salt leads to larger grains. • A more stable perovskite lattice was obtained due to the partly replacement of Zn 2+ and Ac − . • The Ac − group takes superior role than I − and Cl − in passivating the under-coordinated Pb 2+ defects. • The synergistic effect of the Zn(Ac) 2 yields a PCE of 19.32%, enhancement of ∼15%.

High performance sky-blue perovskite light-emitting diodes enabled by a bifunctional phosphate molecule

Defects such as uncoordinated lead ions and surface charged defects are still one of critical issues for perovskite light-emitting diodes (PeLEDs). The presence of these defects can trap excitons, resulting in enhanced nonradiative recombination and thus poor efficiencies of PeLEDs. Defect passivation via passivation agents is an effective way to solve this issue. In this work, we introduce a bifunctional phosphate molecule 6,6′-(ethane-1,2-diyl)bis(dibenzo[c,e][1,2]oxaphosphinine 6-oxide) (DIDOPO) as a passivation agent into the perovskite, where DIDOPO can bind with the perovskite via the chemical interaction between the PO groups and uncoordinated Pb ions. Thus, the incorporation of DIDOPO effectively passivates the defects, leading to improved radiative recombination. Simultaneously, the as-prepared perovskite film produces dense and smooth morphology, which is favorable to good contact with the adjacent charge transport layers and the reduction of leakage current. As a result, the sky-blue PeLEDs modified by DIDOPO show improved efficiency with the maximum external quantum efficiency (EQEmax) of 5.52% and the average EQEmax of 5.09%. Furthermore, attributed to the alkyl chain as the bridge between the phosphate groups, DIDOPO accumulated at the perovskite surface is able to decrease hydrophilic behavior of the perovskite. The PeLEDs containing DIDOPO possess enhanced moisture resistance, remaining ca. 91–92% of the initial EQE after storage for 120 h in ambient atmosphere with the humidity of ca. 40%.

One-step precipitated all-inorganic perovskite QDs from amorphous media for backlighting display and reproducible laser-driven white lighting

Embedded within an inorganic amorphous media, all-inorganic perovskite CsPbX3 (X = Br, I) quantum dots (QDs) overcome the limitation of poor stability for practical application, which has attracted widespread attention. However, the employed thermal treatment strategies for the melting procedure to obtain the amorphous matrix are time- and energy-consuming. Here, we propose an efficient and cost-saving approach for mass production of CsPbBr3 QDs@glass one-step, which maintains the high photoluminescence quantum yield (PLQY 47 %) and narrow full width at half maximum (FWHM 24 nm) of CsPbBr3 QDs. Furthermore, a red shift from 523 to 645 nm of the as-prepared perovskite is achieved by adjusting the halogen composition of the amorphous host from Br to Br/I. Herein, the well-addressed photo- and moisture-stability of the green CsPbBr3 and red CsPbBr1.2I1.8 QDs@glass perovskites endow a 118 % National Television Standards Committee (NTSC) and 88 % Rec. 2020 standards color gamut, combined with a commercial blue GaN chip, for state-of-the-art backlighting display. Moreover, it is found that the performance degradation of the laser-driven white lighting device, causing by the damages of high-power laser irradiation, can be fully recovered after a facile thermal treatment process. We believe that the synthesis strategy opens up a new avenue for the large scale synthesis of high quality perovskite QDs with low cost.

Realize larger grain size of CH3NH3PbI3 film with reduced non-radiative recombination for high performance perovskite solar cells via precursor colloidal size engineering

In CH3NH3PbI3 perovskite solar cells, enhancement grain size of CH3NH3PbI3 to reduce the non-radiative at grain boundaries is an important way to reach high performance perovskite solar cell. However, it is still a challenge to enhance the grain size of CH3NH3PbI3 through a simple and low cost way. In this work, a larger precursor colloidal size is realized through tuning morphology of precursor CH3NH3I using a polar solvent of ethanol during purification, yielding a larger grain size of CH3NH3PbI3 film, and the as-prepared perovskite solar cells are shown to be dramatically increased to 17.49% with an increase in short circuit density, fill factor and open circuit voltage, as compared to that (14.28%) in the control device with CH3NH3I purified by non-polar solvent of diethyl ether. The investigation result showed the increased efficiency of perovskite solar cells prepared by ethanol purification is ascribed to a faster charge transfer at CH3NH3PbI3/TiO2 interface resulting from the reduced grain boundary defects. Our work provides a route for improving the CH3NH3PbI3 device efficiency through a simple yet effective approach.