RESUMO
Flexible sensors and actuators are the basis for realizing the Internet of Everything. This study identifies specific interfacial polarization and filler dispersion challenges in flexible sensors. A novel sandwich-structured flexible sensor with polydimethylsiloxane (PDMS)-filled Nb2CTx as the interlayer and poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)]-filled barium titanate (BTO) as the upper and lower layers was designed and fabricated. The thickness of the interlayer was optimized to be 6.2 µm, resulting in an ultrahigh sensitivity of 16.05 V/N and ultrashort response time of 626 µs. The interlayer achieved an oriented arrangement of the dipoles in the upper and lower piezoelectric films through interfacial polarization, enhancing the piezoelectric output and sensitivity. The proposed mechanism was confirmed by the dielectric properties, local piezoelectric response, cross-sectional potential simulation, and interfacial electrical calculations. Additionally, the sensor effectively distinguishes various body movements, facial micro-expressions, and throat vibrations during vocalization, and can be applied to ultrahigh-sensitive self-powered flexible piezoelectric pressure sensors.
RESUMO
The large open circuit voltage (VOC) loss and phase segregation are two main obstacles hindering the development of wide-bandgap perovskite solar cells (PSCs). Even though substantial progress has been made through crystallization regulation and surface modification on perovskite, the mechanism of VOC loss and phase segregation has rarely been studied. In this paper, we first investigate the halide ions distribution along the out-of-plane direction and find the initial inhomogeneous distribution of halide ions during the crystallization process is an important reason. It leads to the formation of an unfavorable potential well in PSCs, resulting in VOC loss as well as generation of strong strain exacerbating phase segregation. Through introducing melatonin (MT) into perovskite precursors, a homogeneous distribution of halide anions is realized due to the well-regulated crystallization. Consequently, the treated PSCs exhibit an optimized power conversion efficiency (PCE) of 22.88% with a VOC loss as low as 0.38 V, which are the best values for wide-bandgap PSCs up to now.
RESUMO
Highly transparent Ho:Y2O3 ceramics for laser diode lighting were prepared using the vacuum sintering method with 0.3 at.% Nb2O5 as a sintering additive. The microstructures, transmittance, and luminescence properties of the Ho:Y2O3 ceramic samples were investigated in detail. The transmittance levels of all samples with various Ho3+ concentrations reached ~81.5% (2 mm thick) at 1100 nm. Under the excitation of 363 nm (ultraviolet) or 448 nm (blue) light, Ho:Y2O3 transparent ceramic samples showed that green emission peaked at 550 nm. The emission intensity was strongly affected by the concentration of Ho3+ ions, reaching its highest level in the sample doped with 1 at.% Ho3+. The CIE coordinates of the luminescence were in the green region (i.e., the CIE coordinates of the sample doped with 1 at.% Ho3+ were [0.27, 0.53] and [0.30, 0.69], under the excitation of 363 nm and 448 nm light, respectively). The possibility of its application as laser diode lighting was reported. Under the excitation of 450 nm blue laser, the sample doped with 0.5 at.% Ho3+ had the best performance: the saturated luminous flux, lumen efficiency, and the luminescence saturation power densities were 800 lm, 57.7 lm/W, and 17.6 W/mm2, respectively. Furthermore, the materials have high thermal conductivity and mechanical strength due to their host of rare-earth sesquioxide. Thus, Ho:Y2O3 transparent ceramics are expected to be a promising candidate for green-light-emitting devices for solid-state lighting, such as laser diode lighting.