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Enhancing the charge extraction and stability of perovskite solar cells using strontium titanate (SrTiO3) electron transport layer
摘要： Charge transport layers strongly influence the performance of perovskite solar cells (PSCs). To date, compact layers and mesoporous scaffolds of titanium dioxide have emerged as good electron transport layers (ETL), enabling record power conversion efficiencies (PCE). However, these ETLs require sintering above 400 °C, which excludes them from low-temperature applications such as flexible devices and silicon-heterojunction tandems. Furthermore, instability of TiO2 under prolonged exposure to sun light appears to be a critical issue. Here, we present the promising characteristics of low-temperature processed strontium titanate (STO) as an ETL to realize PSCs with 19% PCE. STO is a wide bandgap transparent inorganic perovskite. Compared to other low-temperature processed interlayers, STO reduces the parasitic absorption in the ultraviolet and visible range, improves the electron transport and greatly increases the stability of the devices, retaining ~80% of their initial efficiency after 1000 hours of constant white light illumination.
关键词： perovskite solar cells,stability,low-temperature processing,strontium titanate,electron transport layer
更新于2025-09-12 10:27:22
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Experimental investigations on super-smooth polishing of strontium titanate based ceramics substrates
摘要： Strontium titanate (SrTiO3) is a new type of multi-function electronic ceramic material. SrTiO3 ceramic substrates with a high dielectric constant can be obtained by non-pressurised sintering using ultrathin blanks, which result in the characteristics of thin, soft, brittle and warped. So that SrTiO3 ceramics substrates need to be polished to improve surface quality and dimensional precision before application. In this research, polish experiments with various processing parameters on the surface roughness, the material removal rate and the surface morphologies of SrTiO3 ceramic substrates were conducted. The results show that the SrTiO3 ceramic substrate with a highest quality surface was obtained in the condition: employing a brown polyurethane pad to polish the substrates at a polishing velocity of 45 r/min. Meanwhile, the slurry flow rate, the concentration of the polishing slurry and the polishing pressure were 20 ml/min, 4 wt% and 15.043 kPa, respectively, which rates with an overall and a partial surface roughness of Ra 0.01 μm and Ra 4 nm, respectively. While some new micro-scratches were generated on the surface of the SrTiO3 ceramics substrate in the polishing process because the embedding and scratching of abrasive particle led to expose the inherent pores and grain boundaries.
关键词： ceramic substrate,material removal rate,strontium titanate,polishing,surface roughness
更新于2025-09-10 09:29:36
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Investigation of the Eightwise Switching Mechanism and Its Suppression in SrTiO <sub/>3</sub> Modulated by Humidity and Interchanged Top and Bottom Platinum and LaNiO <sub/>3</sub> Electrode Contacts
摘要： Memristive devices are hardware components for applications in neuromorphic computing, memories, and logic computation. This work contributes to the ongoing debate on the switching mechanism of eightwise polarity in SrTiO3-based resistive switches. Specifically the effect of atmospheric humidity on the materials defect chemistry and switching properties is considered. Asymmetric devices are designed by exchanging the top and bottom positions of Pt and LaNiO3 electrodes allowing for a separate analysis of the top and the bottom metal-oxide interfaces. Under dry atmospheres the switching hysteresis is enhanced with a top Pt contact and suppressed with a bottom Pt contact. It is argued that the buried position and dense microstructure of the bottom platinum impedes an oxygen vacancy driven switching mechanism. Under humid atmospheres eightwise switching occurs in both devices suggesting the presence of two switching mechanisms within the same eightwise switching polarity, namely, oxygen vacancy and hydroxide ion enabled switching. The findings help develop strategies to suppress eightwise switching by burying the active metal-oxide interface and ensuring dense electrode microstructures. Suppression of switching mechanisms relying on exchange with the environment is desirable for technological implementation of resistive switches and for strategies in stacking of memristive devices for memory and for neuromorphic hardware.
关键词： strontium titanate,humidity,resistive switching,eightwise polarity
更新于2025-09-10 09:29:36
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[IEEE 2017 IEEE MTT-S International Microwave and RF Conference (IMaRC) - AHMEDABAD, India (2017.12.11-2017.12.13)] 2017 IEEE MTT-S International Microwave and RF Conference (IMaRC) - Frequency Agile Monolithic Inset Fed Microstrip Patch Antenna Based on Barium Strontium Titanate (Ba<inf>x</inf>Sr<inf>1-x</inf>TiO<inf>3</inf>) Ferroelectric Substrate
摘要： This paper demonstrates frequency agile inset fed microstrip patch antenna built on Barium Strontium Titanate (BST: BaxSr1-xTiO3) substrate. Concept and design methodology of X-band frequency agile microstrip patch antenna monolithically integrated with coplanar capacitor, bias tee and DC block capacitor are discussed. Antenna design is carried out on 0.5μm thick Ba0.6Sr0.4TiO3 hosted by 1mm Quartz substrate. C-V characterization of this BST film is also performed and presented. Microstrip antenna on BST film has been realized using SolGel method and shows 50MHz frequency tunability during measurement for bias voltage variation from 0V to 154V. The gain and pattern purity of the antenna is maintained over this bandwidth.
关键词： Frequency agility,Microstrip Patch Antenna,Barium Strontium Titanate,Coplanar capacitor
更新于2025-09-10 09:29:36
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Epitaxial processing optimization and photoluminescence spectra of CdTe thin films grown on highly dissimilar SrTiO3 (001) by molecular beam epitaxy
摘要： Single crystalline CdTe epitaxial layers (CTELs) are grown on a highly dissimilar (001) SrTiO3 (STO) by molecular beam epitaxy. The optimized growth temperature is determined to be in the range of 210 °C–270 °C. The crystalline structures of the CTELs are characterized by X-ray di?raction (XRD). The lattice parameters of the CTELs are revealed by the in-plane and out-of-plane reciprocal space mapping, electron microscopy and electron di?raction, and the epitaxial relationships between ?lm and substrate are further summarized as: (111)CdTe || (001)STO, [1?10]CdTe || [010]STO and [11?2]CdTe || [100]STO. The optimized full width at half maximum is yielded to be ~108 arcsec. The high crystalline quality and sharp interface are highlighted by the appearance of well-de?ned fringes of the XRD patterns, electron microscopy and photoluminescence spectra. Finally, the possible growth mechanisms are discussed and compliant epitaxial mechanism can well account for the epitaxial growth of the CdTe(111)/STO(001) epitaxial system. The achievement of the epitaxial growth of the CTELs on (001) STO with atomic ?atness and high-crystalline quality will avail to the potential application in photo-electric devices and the further epitaxy of the Hg1-xCdxTe-based infrared detector materials.
关键词： Photoluminescence,Cadmium telluride,Strontium titanate,Epitaxial layers,Molecular beam epitaxy,Perovskite substrate
更新于2025-09-10 09:29:36
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Conductivity of Iron-doped Strontium Titanate in the Quenched and Degraded States
摘要： The electrical behavior of iron-doped strontium titanate (Fe:SrTiO3) single crystals equilibrated at 900 °C and quenched below 400 °C at various oxygen partial pressures ( ) was investigated via impedance spectroscopy and compared to defect chemistry models. Fe:SrTiO3 annealed and quenched between and Pa exhibits a conduction activation energy (EA) around 0.6 eV, consistent with ionic conduction of oxygen vacancies. However, sudden changes in EA are found to either side of this range; a transition from 0.6 to 1 eV is found in more oxidizing conditions, while a sudden transition to 1.1 and then 0.23 eV is found in reducing .These transitions, not described by the widely used canonical model, are consistent with predictions of transitions from ionic to electronic conductivity, based on first principles point defect chemistry simulations. These models demonstrate that activation energies in mixed conductors may not correlate to specific conduction mechanisms, but are determined by the cumulative response of all operative conduction processes and are very sensitive to impurities. A comparison to electrically degraded Fe:SrTiO3 provides insight into the origins of the conductivity activation energies observed in those samples.
关键词： defect chemistry,Strontium titanate,conductivity,resistance degradation
更新于2025-09-09 09:28:46
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Optical Characteristics of Strontium Titanate Films Obtained by the Sol–Gel Method
摘要： Using data of multiangle spectrophotometry and spectral ellipsometry in the UV and visible ranges, spectra of the refractive indices and absorption coefficients and width of the forbidden band of one- and five-layer strontium titanate films obtained by the sol–gel method have been calculated. Layer-by-layer deposition of sol on quartz substrates, from one to five layers, leads to an increase in film porosity from 4 to 33%. This causes a decrease in the refractive indices in the middle part of the visible spectrum from 2.33 to 1.87, which leads to a decrease in the reflectance and an increase in the transmittance or transparency of five-layer films. With an increase in the heating temperature of such films from 500 to 750°C, a shift of the absorption band maximum from 239 to 253 nm takes place and the optical width of the forbidden band decreases from 4.63 to 4.20 eV. The absorption band maximum of the single-layer film falls on the wavelength of 252 nm, and its optical width of the forbidden band is 3.96 eV.
关键词： Strontium titanate films,optical characteristics,forbidden band width,sol–gel method,refractive indices,absorption coefficients
更新于2025-09-09 09:28:46
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The role of point defects and defect gradients in flash sintering of perovskite oxides
摘要： The present study investigates the impact of point defects and their redistribution on the flash sintering process. Strontium titanate was chosen as a model system for the group of perovskite ceramics. The characteristics of flash sintering of strontium titanate were analyzed with different acceptor dopant concentrations. The onset of flash sintering was found to be dependent on the acceptor dopant concentration, as expected by the increasing conductivity. A gradient in the microstructure was found after flash sintering with larger grain sizes at the negative electrode. TEM-EDS measurements indicated Ti enrichment at the positive electrode for undoped strontium titanate and strong acceptor segregation for doped strontium titanate. In contrast, grain boundaries at the negative electrode were found to be stoichiometric for the undoped case and the acceptor segregation was less obvious for the doped case. Based on these results and the space charge behavior of strontium titanate, we infer that a gradient of the oxygen vacancy concentration is induced by the electric field during flash sintering: at the positive electrode the oxygen vacancy concentration is higher than at the negative electrode. For strontium titanate it is well known that a high oxygen vacancy concentration reduces the space charge and, hence, acceptor segregation, which agrees well with the experimental findings. Overall, the present study highlights the importance of point defect gradients and space charge for flash sintering of strontium titanate, which may be applicable for many other functional ceramics.
关键词： Flash sintering,Space charge,Non-stoichiometry,Strontium titanate,Point defects
更新于2025-09-04 15:30:14
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Preparation and Characterization of Ba1-xSrxTiO3 by Sol-Gel Method
摘要： Barium strontium titanate (BST) with formula (Ba1-xSrxTiO3) has been synthesized by sol-gel method with different stoichiometric compositions (x = 0.3, 0.4, 0.5, 0.6). The raw materials which used to prepare compounds are (Ba,Sr) acetate as a source (Ba,Sr) and titanate isopropoxide source. The FE-SEM images showed that the particles size reduced from 464 to 13 nm when strontium concentration increased from 0.3 to 0.6. The X-ray diffraction studies have confirmed that Ba0.7Sr0.3TiO3 sample have the tetragonal phase while remaining samples have a cubic phase. The intensity of the major peaks were decreased and shifted toward higher 2θ angles when Sr2+ ions increases.
关键词： Barium strontium titanate,Curie Temperature,Ferroelectric materials,Perovskite structure
更新于2025-09-04 15:30:14