Perovskite Template Research Articles

New Insights into MAI Additives in 2D-Assisted 3D Controlled Crystallization Toward High-Quality α-Phase FAPbI3 Perovskites.

The highly oriented 2D perovskite templates of n = 1 have typically been created to attain controllable and oriented crystallization of 3D α-phase formamidinium lead triiodide (α-FAPbI3) perovskites. However, the role of methylammonium iodide (MAI), a widely used α-FAPbI3 phase stabilizer, in regulating the growth dynamics of 2D/3D perovskites is generally ignored. Herein, Ruddlesden-Popper type n = 1 2D octylammonium lead iodide(OA2PbI4) perovskites are added into FAPbI3 precursor solution. The template of n = 2 (OA2MAPb2I7), which is spontaneously constructed by the mixture of n = 1 2D and methylammonium chloride (MACl), acts as a skeleton to template the epitaxial growth of α-FAPbI3. However, the volatilization of MACl inevitably causes damage to the 2D structure during thermal annealing. This study reveals that small amounts of less volatile MAI additive enables the creation of stable 2D template, leading to more controlled vertical orientation crystallization. Consequently, the high-quality mixed-dimensional perovskite film delivers a high efficiency of 24.19% together with improved intrinsic stability. This work provides an in-depth understanding of 2D-assisted controlled epitaxial growth of α-FAPbI3.

Layer-number tailoring and template-induced orientation control of 2D perovskites on 3D perovskites by adopting the Dion–Jacobson phase

Orientation-controlled 2D perovskites consisting of octahedral monolayers have been realized on 3D perovskites. By bar-coating a Dion–Jacobson (DJ) phase 2D perovskite precursor solution onto 3D perovskite thin films, the conversion of the top layer of 3D perovskite to 2D perovskite was promoted, and the optimal 2D/3D heterostructure could be fabricated. The orientation of the DJ 2D perovskite could be controlled horizontally or obliquely according to the 3D perovskite template thin films; the 2D perovskite was obliquely oriented on (200)/(112)-oriented CH3NH3PbI3, and horizontally oriented on (110)-oriented CH3NH3PbI2.5Cl0.5. This approach would boost the stability and power conversion efficiency of 2D/3D heterostructures.

Improved out-coupling efficiency of organic light-emitting diodes using micro-sized perovskite crystalline template

In this study, we demonstrated that the out-coupling efficiency of organic light-emitting didoes (OLEDs) is enhanced using external light extraction film obtained from the CH 3 NH 3 PbBr 3 (MAPbBr 3 ) perovskite template. We found that the perovskite crystalline is very suitable to be used as a template because by changing the process conditions such as the solvent type, its micro-scale crystal growth can be achieved. In addition, the perovskite template can be used repeatably, allowing multiple films to be imprinted on one template. By attaching the imprinted polydimethylsiloxane (PDMS) films on the bottom-emitting OLED, we found that the light-emitting performances are improved. The surface morphology of the perovskite template as well as the imprinted PDMS light extraction film were investigated with an optical microscope and a scanning electron microscope (SEM). OLEDs equipped with PDMS light extraction films imprinted on 20 wt% and 30 wt% MAPbBr 3 templates show improved external quantum efficiency by about 30.9% and 11.1%, respectively. It is demonstrated that the transmittance and haze characteristics of films are not significantly changed by imprinting from templates with different concentrations. Rather, the improvement in the out-coupling efficiency of the OLEDs is largely attributed to the fill factor of the crystals of the film and not the light scattering effect from the film. We demonstrated that the out-coupling efficiency of organic light-emitting didoes (OLEDs) is enhanced using external light extraction film obtained from the CH3NH3PbBr3 (MAPbBr3) perovskite template. We found that the perovskite crystalline is very suitable to be used as a template because by changing the process conditions such as the solvent type, its micro-scale crystal growth can be achieved. In addition, the perovskite template can be used repeatably, allowing multiple films to be imprinted on one template. By attaching the imprinted polydimethylsiloxane (PDMS) films on the bottom-emitting OLED, we found that the light-emitting performances are improved. The surface morphology of the perovskite template as well as the imprinted PDMS light extraction film were investigated with an optical microscope and a scanning electron microscope (SEM). OLEDs equipped with PDMS light extraction films imprinted on 20 wt% and 30 wt% MAPbBr3 templates show improved external quantum efficiency by about 30.9% and 11.1%, respectively. It is demonstrated that the transmittance and haze characteristics of films are not significantly changed by imprinting from templates with different concentrations. Rather, the fill factor is reduced when the PDMS light extraction film is imprinted on templates with high concentration. Thus, the improvement in the out-coupling efficiency of the OLEDs is largely attributed to the fill factor of the crystals of the film and not the light scattering effect from the film. The low-cost, and simple fabrication process for the light extraction films pave the way for commercial application in advance OLEDs. • External light-extraction film is obtained with perovskite template. • Micro-scale crystal template is prepared and PDMS is imprinted. • The EQE enhancement of 30.9% is demonstrated. • Fill factor of template is investigated.

Virus-like hollow mesoporous silica nanoparticles for cancer combination therapy

Virus-like nanostructures could involve their interaction with biological hosts, as well as adaptive immune responses. Herein, imitating the intrinsic structure of virus, we formulated novel virus-like hollow mesoporous silica nanoparticles (VH-MSNs) by using self-consuming perovskite template. The unique topological structure on the surface of nanoparticles could enhance cellular uptake and amplify the immune response. By loading doxorubicin (DOX) on nanoparticles, we achieved a combination of chemotherapy and immunotherapy. This study provides a promising platform with superior cellular uptake property for drug delivery and a basis for the study of the effect of surface physical structure on the nanocarriers.

Solid-phase hetero epitaxial growth of \u03b1-phase formamidinium perovskite

Conventional epitaxy of semiconductor films requires a compatible single crystalline substrate and precisely controlled growth conditions, which limit the price competitiveness and versatility of the process. We demonstrate substrate-tolerant nano-heteroepitaxy (NHE) of high-quality formamidinium-lead-tri-iodide (FAPbI3) perovskite films. The layered perovskite templates the solid-state phase conversion of FAPbI3 from its hexagonal non-perovskite phase to the cubic perovskite polymorph, where the growth kinetics are controlled by a synergistic effect between strain and entropy. The slow heteroepitaxial crystal growth enlarged the perovskite crystals by 10-fold with a reduced defect density and strong preferred orientation. This NHE is readily applicable to various substrates used for devices. The proof-of-concept solar cell and light-emitting diode devices based on the NHE-FAPbI3 showed efficiencies and stabilities superior to those of devices fabricated without NHE.

Fabrication of PbBi4Ti4O15 microplatelets with different TiO2 reactants

Platelet PbBi4Ti4O15 (PBIT) microcrystals were fabricated by molten salt methods using different TiO2 crystal forms (anatase and rutile) as the reactants. The results showed that the pure PBIT phase can be obtained by using rutile as the reactant, while the PBIT and TiO2 phases coexisted when using anatase as the reactant. In comparison to anatase, the co-topping connection of rutile has better stability and accelerates the nucleation growth rate in a molten salt environment. Thus, PBIT microplatelets with the good crystallinity and plate-like morphology (aspect ratio of ~27) can be obtained when rutile is used as the reactant. Specifically, when using rutile as the reactant, a maximum d33∗ of ~153 pm/V can be obtained, which may potentially allow the fabrication of anisotropic perovskite templates for textured ceramics.

Fabrication of Efficient and Stable CsPbI3 Perovskite Solar Cells through Cation Exchange Process

AbstractInorganic lead halide perovskites have attracted attention due to their tolerance to higher processing temperature and higher bandgap suitable for tandem solar cell application. Not only do they improve cell stability and efficiency, they also reveal many interesting and un‐anticipated material qualities. This work reports a simple cation exchange growth (CEG) method for fabricating inorganic high‐quality cesium lead iodide (CsPbI3) by adding methylammonium iodide (MAI) additive in the precursor. X‐ray diffraction results reveal a multi‐stage film formation process whereby i) MAPbI3 perovskite first formed that acts as a perovskite template for ii) subsequent ion exchange whereby the MA+ ions in the MAPbI3 are replaced by Cs+ (as temperature ramps up) and iii) form g‐phase perovskite CsPbI3. Optical microscopy, photoluminescence, and electrical characterizations reveal that the CEG process produces high‐quality film with better absorption, uniform and dense film with better interface, lower defects, and better stability. Using the CEG approach, the power conversion efficiency of the best CsPbI3 solar cell is significantly increased up to 14.1% for the device fabricated using 1.0 m MAI additive. The outcome is beneficial for further improvement of inorganic perovskite solar cells and their application in perovskite‐silicon tandem devices.

Characterization of thick bismuth ferrite–lead titanate films processed by tape casting and templated grain growth

The templated grain growth technique was used to synthesise textured 60BiFeO3–40PbTiO3 (60:40BFPT). Both Aurivillius (Bi4Ti3O12, PbBi4Ti4O15) and perovskite templates (BaTiO3, SrTiO3) were used to prepare 60:40BFPT. Only BaTiO3 templates were found to successful impart a texture to the ceramic matrix. In the case of perovskite templates, ferroelectricity was evident from saturated polarisation hysteresis loops. Saturated polarisation loops were achieved due to the substitution of Ba2+ or Sr2+, which reduces the coercive field. SrTiO3 and BaTiO3 templated ceramics showed remanent polarisation of 30 and 36μC/cm2, respectively. Aurivillius templates did not generate ferroelectric materials. Because of their high chemical stability in this system, BaTiO3 templates appear to be the best candidate for fabricating textured BFPT by the reactive templated grain growth method.

Layered organic–inorganic hybrid perovskites: structure, optical properties, film preparation, patterning and templating engineering

Organic–inorganic perovskites are a class of interesting compound in the perovskite family due to their unique structures of alternately stacking sheets of organic and inorganic components on the molecular scale. In this highlight, the basic knowledge and recent advances in organic–inorganic perovskites are reviewed with particular emphasis on the feature work including: the novel <110>- and <111>-oriented perovskite structures, synthesis, film preparation, patterning methods and optoelectronic properties of hybrid perovskites. Moreover, the small functional organic molecules can be templated into a regular arrangement by the inorganic perovskite framework. This unique material with nature-formed lamellar structure has the potential to be used as a template to create novel derivatives and bring about unique physical properties. Some interesting examples, such as intercalated polymer and silica network by topochemical polymerisation, fabrication of disk-like semiconductor nanocrystals and metal nanoparticles by hybrid perovskite templates are described.

Growth and Characterizations of Relaxor-Based Pb(Mg&lt;sub&gt;1/3&lt;/sub&gt;Nb&lt;sub&gt;2/3&lt;/sub&gt;)O&lt;sub&gt;3&lt;/sub&gt;-PbTiO&lt;sub&gt;3&lt;/sub&gt; Thin Films by Sol-Gel Method

Relaxor-based 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (PMN-PT) thin films were grown epitaxially on silicon substrates by sol-gel method and PbO cover coat technique, and investigated by x-ray diffraction, auger electron spectroscopy, scanning electron microscopy, and transmission electron microscopy. The phase development and microstrure evolution of the PMN-PT film were significantly affected by the final annealing temperature and time. A perovskite PMN-PT film was obtained after annealing at 850oC for 1 min. Then, highly &lt;100&gt;-oriented and textured PMN-PT films could be achieved by using a LaNiO3 perovskite template.

Superconductivity in a layered perovskite without copper

FOLLOWING the discovery of superconductivity at ∼30 K in La2−xBaxCuO4 (ref. 1), a large number of related compounds have been found that are superconducting at relatively high temperatures. The feature common to all of these materials is a layered crystal structure based on a perovskite template and containing planar networks of copper and oxygen. This raises the question of whether superconductivity can occur in layered perovskites that do not contain copper. To the best of our knowledge, no such material has been found to date, despite nearly a decade of searching. We describe here the discovery of superconductivity in Sr2RuO4, a layered perovskite isostructural with La2−xBaxCuO4 (Fig. 1). Our results demonstrate that the presence of copper is not a prerequisite for the existence of superconductivity in a layered perovskite. But the low value of the superconducting transition temperature (Tc = 0.93 K) points towards a special role for copper in the high-temperature superconductors.