Abstract
Rapid advancements in perovskite materials have led to potential applications in various optoelectronic devices, such as solar cells, light-emitting diodes, and photodetectors. Due to good ...photoelectric properties, perovskite enables low-cost and comparable performance in terms of responsivity, detectivity, and speed to those of the silicon counterpart. In this work, we utilized triple cation perovskite, well known for its high performance, stability, and wide absorption range, which is crucial for broadband photodetector applications. To achieve improved detectivity and faster response time, graded multilayer perovskite absorbers were our focus. Sequential spray deposition, which allows stacked perovskite architecture without disturbing lower perovskite layers, was used to generate single, double, and triple-layer perovskite photodetectors with proper energy band alignment. In this work, we achieved a record on self-powered perovskite photodetector fabricated from a scalable spray process in terms of EQE and responsivity of 65.30% and 0.30 A W
-1
. The multilayer devices showed faster response speed than those of single-layer perovskite photodetectors with the champion device reaching 70 µs and 88 µs for rising and falling times. The graded band structure and the internal electric field generated from perovskite heterojunction also increase specific detectivity about one magnitude higher in comparison to the single-layer with the champion device achieving 6.82 × 10
12
cmHz
1
/
2
W
−
1
.
With growing population, vertical spaces from skyscrapers are vast. Semi-transparent solar cells enable an effective pathway for vertical energy harvesting. With composition tunability, perovskite ...materials can be designed with different transparencies and colors. In this work, an ultra-high bandgap layered triple cation perovskite system was developed for the first time to meet the demand of clear optoelectronic applications; low dimensional triple cation perovskite thin films were fabricated using perovskite with the formula (PEA)
(Cs
MA
FA
)
(Pb)
(Cl
Br
)
, 0 ≤ x ≤ 0.02 with DMSO as the appropriate solvent. The absorption edge of the material is around 410-430 nm, achieving great transparency to visible light. The structural, optical, and photovoltaic performances of the clear perovskite materials are explored with the variation of Cs contents via CsBr. The relation between thickness, transparency, and optoelectronic properties of the clear perovskite materials along with other physical properties were investigated. The highest photovoltaic conversion efficiency (PCE) of clear perovskite solar cells with 1.5% Cs was achieved to be 0.69% under xenon lamp irradiation at 100 mW/cm
(1.5 mW/cm
of UVA within 100 mW/cm
) and 5.24% under 365 nm UV irradiation at 2.4 mW/cm
. Photoresponsivity, external quantum efficiency (EQE), and detectivity were also determined for photodetector applications.
Hydrogenated amorphous carbon (a-C:H) films have optical and electrical properties that vary widely depending on deposition conditions; however, the electrical conduction mechanism, which is ...dependent on the film structure, has not yet been fully revealed. To understand the relationship between the film structure and electrical conduction mechanism, three types of a-C:H films were prepared and their film structures and electrical properties were evaluated. The sp2/(sp2 + sp3) ratios were measured by a near-edge X-ray absorption fine structure technique. From the conductivity–temperature relationship, variable-range hopping (VRH) conduction was shown to be the dominant conduction mechanism at low temperatures, and the electrical conduction mechanism changed at a transition temperature from VRH conduction to thermally activated band conduction. On the basis of structural analyses, a model of the microstructure of a-C:H that consists of sp2 and sp3-bonded carbon clusters, hydrogen atoms and dangling bonds was built. Furthermore, it is explained how several electrical conduction parameters are affected by the carrier transportation path among the clusters.
In this letter, we report on the simple process of preparing perovskite oxide SrMnO
3
and the studying of the size effect on electrochemical properties for high-performance supercapacitor electrode. ...The high-crystalline micro-sized and nano-sized perovskite oxide SrMnO
3
particles were successfully synthesized by a simple solid-state reaction, followed by a simple size reduction using high-energy ball milling. The electrochemical properties of the SrMnO
3
had intriguing results on both sizes of particle, especially when comparing between before and after cycles. After a size reduction, the specific capacitance of the particles increased approximately twofold. Interestingly, the micro-sized SrMnO
3
gained ∼500% its initial specific capacitance after 3000 successive cycles due to electrochemical nano-feature activation and oxygen-vacancy production, while the specific capacitance for the nano-sized SrMnO
3
remained almost unchanged. Our work suggested a cost-effective and simple technique for high-performance perovskite-based supercapacitor electrodes by achieving the desired performance.
Hydrogenated amorphous carbon (a-C:H) films are only empirically known to be decomposed by heating, and this heat resistance is expected to be dependent on the structure of the film. To understand ...the decomposition processes and their uniformity, the thermal decomposition characteristics of two types of a-C:H film were investigated after the structural determination of the sp2/(sp2 + sp3) ratios and hydrogen contents. The mass of the gas released by thermal decomposition of the a-C:H films was detected by evaluation of the thermal desorption spectroscopy to determine the starting temperature the film with high hydrogen content started to desorb hydrogens at 400 °C and hydrocarbons at 750 °C. The film with low hydrogens started to desorb decomposition gases at 750 °C. Moreover, uniform decomposition of the films was observed using synchrotron-based X-ray photoemission electron microscopy (X-PEEM) and near edge X-ray absorption fine structure (NEXAFS) spectroscopy. The thermal decomposition of a-C:H films with uniform film structure proceeds relatively uniformly, and the mechanism of thermal decomposition of the films depends on the source materials of the films. The thermal decomposition proceeds uniformly at the micron scale when the initial structure is uniform.
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•Thermal decomposition on the hydrogenated amorphous carbon films was investigated.•The mass of gas released by thermal decomposition of the films was detected by TDS.•Starting temperature of thermal decomposition depends on the film structure.•Decomposition uniformity of sp2/sp3 carbon ratio was observed using X-PEEM and NEXAFS.•The thermal decomposition of a-C:H films with a uniform structure proceeds relatively uniformly.
With high efficacy for electron-photon conversion under low light, perovskite materials show great potential for indoor solar cell applications to power small electronics for internet of things ...(IoTs). To match the spectrum of an indoor LED light source, triple cation perovskite composition was varied to adjust band gap values via Cs and Br tuning. However, increased band gaps lead to morphology, phase instability, and defect issues. 10% Cs and 30% Br strike the right balance, leading to low-cost carbon-based devices with the highest power conversion efficiency (PCE) of 31.94% and good stability under low light cycles. With further improvement in device stack and size, functional solar cells with the ultralow hysteresis index (HI) of 0.1 and the highest PCE of 30.09% with an active area of 1 cm2 can be achieved. A module from connecting two such cells in series can simultaneously power humidity and temperature sensors under 1000 lux.
Display omitted
•Triple cation perovskite with 10% Cs and 30% Br is fit for collecting indoor light•High Cs/Br leads to wrinkle morphology and poor interface between perovskite and HTL•Carbon-based solar cell with ultralow HI of 0.1 and PCE of 30.09% can be achieved•Connecting 2 devices (1 cm2 active area) in series can power IoTs under 1000 lux
Devices; Energy materials; Materials science
The compositions and bonding states of the amorphous hydrogenated carbon films at various thicknesses were evaluated via near-edge X-ray absorption fine-structure (NEXAFS) and elastic recoil ...detection analysis combined with Rutherford backscattering spectrometry. The absolute carbon sp 2 contents were determined to decrease to 65% from 73%, while the hydrogen contents increase from 26 to 33 at.% as the film thickness increases. In addition, as the film thickness increases, the π ⁎ (C=C), σ ⁎ (C–H), σ ⁎ (C=C), and σ ⁎ (C≡C) bonding states were found to increase, whereas the π ⁎ (C≡C) and σ ⁎ (C–C) bonding states were observed to decrease in the NEXAFS spectra. Consequently, the film thickness is a key factor to evaluate the composition and bonding state of the films.
The dissolution of the microalloying elements in high strength low alloy steels is a cause of longer slab reheating time before hot forming processes compared with those for carbon steels. This is to ...ensure that all the necessary microalloying elements are dissolved and available for the precipitation hardening during and after the hot forming processes. In order to decrease the enormous amount of the reheating energy, which is the only heat required in the hot forming process, this works selects a high strength low alloy steel containing vanadium and analyses the dissolution kinetics by means of X-ray absorption spectroscopy (XAS). The XAS scans for other elements, i.e., titanium and nitrogen have been carried out and discussed for the possibility of the technique to investigate precipitates in microalloyed steels.
Vanadium shows rapid dissolution kinetics that as soon as a lower reheating temperature of 1200 °C is reached, most of it is dissolved into the solid solution. This is opposite to titanium whose most fraction is still in TiN after long reheating time at higher temperature in accordance with the application of TiN for the grain boundary pinning during reheating. X-rays absorption near edge structure (XANES) analysis of nitrogen shows different form of spectra before and after the reheating process. This indicates that the change in the coordination around the central nitrogen atoms takes place during the reheating interval.
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