Solar-heating catalysis has the potential to realize zero artificial energy consumption, which is restricted by the low ambient solar heating temperatures of photothermal materials. Here, we propose ...the concept of using heterostructures of black photothermal materials (such as Bi
Te
) and infrared insulating materials (Cu) to elevate solar heating temperatures. Consequently, the heterostructure of Bi
Te
and Cu (Bi
Te
/Cu) increases the 1 sun-heating temperature of Bi
Te
from 93 °C to 317 °C by achieving the synergy of 89% solar absorption and 5% infrared radiation. This strategy is applicable for various black photothermal materials to raise the 1 sun-heating temperatures of Ti
O
, Cu
Se, and Cu
S to 295 °C, 271 °C, and 248 °C, respectively. The Bi
Te
/Cu-based device is able to heat CuO
/ZnO/Al
O
nanosheets to 305 °C under 1 sun irradiation, and this system shows a 1 sun-driven hydrogen production rate of 310 mmol g
h
from methanol and water, at least 6 times greater than that of all solar-driven systems to date, with 30.1% solar-to-hydrogen efficiency and 20-day operating stability. Furthermore, this system is enlarged to 6 m
to generate 23.27 m
/day of hydrogen under outdoor sunlight irradiation in the spring, revealing its potential for industrial manufacture.
The trivalent lanthanides have been broadly utilized as emitting centers in persistent luminescence (PersL) materials due to their wide emitting spectral range, which thus attract considerable ...attention over decades. However, the origin of the trivalent lanthanides' PersL is still an open question, hindering the development of excellent PersL phosphors and their broad applications. Here, the PersL of 12 kinds of the trivalent lanthanides with the exception of La
, Lu
, and Pm
is reported, and a mechanism of the PersL of the trivalent lanthanides in wide bandgap hosts is proposed. According to the mechanism, the excitons in wide bandgap materials transfer their recombination energy to the trivalent lanthanides that bind the excitons, followed by the generation of PersL. During the PersL process, the trivalent lanthanides as isoelectronic traps bind excitons, and the binding ability is not only related to the inherent arrangement of the 4f electrons of the trivalent lanthanides, but also to the extrinsic ligand field including anion coordination and cation substitution. Our work is believed to be a guidance for designing high-performance PersL phosphors.
Recently, vertically oriented few-layer 2D materials prepared by chemical vapor deposition (CVD) have attracted much attention due to their attractive properties. However, the integration of these ...materials as heterojunctions in optoelectronic sensors has been rarely reported. In this paper, large-area, high crystalline quality, and vertically oriented few-layered MoS2 (V-MoS2) nanosheets were synthesized and transferred successfully onto a silicon substrate to form a V-MoS2/Si heterojunction photodetector. The photodetector exhibits high photoelectric performances in a wide broadband ranging from visible to near-infrared with a photoresponsivity of up to 908.2 mA W−1, and a detectivity of up to 1.889 × 1013 Jones. More importantly, an unprecedented response speed of (rise time ∼ 56 ns, fall time ∼ 825 ns) was found in the photodetector by time response measurements, which is the best result achieved so far in any other 2D-based photodetectors or phototransistors. These excellent performances can be ascribed to the strong light absorption and the quick longitudinal intralayer carrier transport speed of the V-MoS2 nanosheets as well as the good heterojunction formed between V-MoS2 and Si. This intriguing vertical oriented structure in combination with both ultrafast time response and ultrahigh detectivity in the V-MoS2/Si heterojunction provide great potential for application in optoelectronic devices.
The Cu(In,Ga)Se2 (CIGS) heterojunction, as a mature and high efficiency thin‐film solar cell, is rarely studied as a photodetector, especially in flexible substrates. In this paper, the structure of ...an ITO/ZnO/CdS/CIGS/Mo heterojunction is grown on the polyimide (PI) substrate to form a flexible CIGS heterojunction photodetector. The photodetector can work in a very wide band ranging from 350 to 1200 nm with responsivity up to 1.18 A W−1 (808 nm), detectivity up to 6.56 × 1010 Jones (cmHz1/2 W−1), and response time of 70 (/88) ms, respectively. Moreover, the piezophototronic effect is first used to investigate performance modulation of this device by effectively controlling the separation and transport of carriers at the interface of CdS/ZnO. Interestingly, by externally applying a 0.763% tensile strain, the photoresponsivity and detectivity of the photodetector exhibit a decrease from 1.18 to 0.88 A W−1, and from 6.56 × 1010 to 4.81 × 1010 Jones, respectively, while under a –0.749% externally static compressive strain, the photoresponsivity could be enhanced by ≈75.4% with a maximum of 2.07 A W−1, and the detectivity is improved by ≈66.1% with its peak value up to 10.9 × 1010 Jones. Meanwhile, the response time can be modulated from 99(/116) to 41.3(/42.6) ms. This work suggests that the CIGS heterojunction has great potential in novel applications for piezophototronic sensors and also gives a hint to modulate the performance of other multilayer heterostructures via the piezotronic effect.
The structure of an ITO/ZnO/CdS/ Cu(In,Ga)Se2(CIGS)/Mo heterojunction is grown on a polyimide substrate to form a flexible CIGS heterojunction photodetector. The photodetector can work in a very wide band ranging from 350 to 1200 nm with high photoresponse performance. More importantly, by exerting the piezophototronic effect, the photoresponse performance can be modulated considerably with photoresponsivity changing from 0.88 to 2.07 A W−1, detectivity changing from 4.81 × 1010 to 10.9 × 1010 Jones, and response time from 99(/116) to 41.3(/42.6) ms, respectively.
The post deposition treatment of CsF (CsF-PDT) plays an important role in improving the performance of CIGS solar cells. However, the doping mechanism of Cs-PDT is controversial. To further clarify ...it, the material properties of the CIGS thin film and photovoltaic characteristics of the devices with different amount of CsF doping are investigated in this paper. It can be demonstrated that the surface morphology, chemical properties and electrical structure of the absorber after CsF-PDT are similar to those of samples after KF-PDT and RbF-PDT. Especially, analogous wide band gap compound CsInSe2 is formed at the surface of the absorber, which can significantly reduce the interfacial recombination between the buffer layer and absorber. However, the measurement results indicate that the distribution and role of Cs in the absorber are somewhat different from those previously reported. Firstly, the entry of Cs does not promote the reduction of Na, but makes more Na enter the absorber. Secondly, the Cs atoms entering the film not only locate at the grain boundary but also enter the grains. Therefore, they can passivate the defects both at the grain boundary and grain interior, improving the hole carrier concentration and minority carrier lifetime. Finally, when excess Cs atoms enter the grain, the lattice constants and texture of the film transform significantly. In this case, the new defects (40 meV and 420 meV) will be generated in the film, which deteriorates the device performance.
Bottom-up Photonic Crystal Lasers Scofield, Adam C; Kim, Se-Heon; Shapiro, Joshua N ...
Nano letters,
12/2011, Letnik:
11, Številka:
12
Journal Article
Recenzirano
The directed growth of III–V nanopillars is used to demonstrate bottom-up photonic crystal lasers. Simultaneous formation of both the photonic band gap and active gain region is achieved via ...catalyst-free selective-area metal–organic chemical vapor deposition on masked GaAs substrates. The nanopillars implement a GaAs/InGaAs/GaAs axial double heterostructure for accurate, arbitrary placement of gain within the cavity and lateral InGaP shells to reduce surface recombination. The lasers operate single-mode at room temperature with low threshold peak power density of ∼625 W/cm2. Cavity resonance and lasing wavelength is lithographically defined by controlling pillar pitch and diameter to vary from 960 to 989 nm. We envision this bottom-up approach to pillar-based devices as a new platform for photonic systems integration.
Topological insulators, such as Bi2Te3, have been confirmed to exhibit plasmon radiation over the entire visible spectral range. Herein, we fabricate bullseye nanoemitters, consisting of a central ...disk and concentric gratings, on the Bi2Te3 nanoflake. Due to the existence of edge plasmon modes, Bi2Te3 bullseye nanostructures are possible to converge light towards the central disk. Taking advantage of the excellent spatial resolution of cathodoluminescence (CL) characterization, it has been observed that plasmonic behaviors depend on the excitation location. A stronger plasmonic intensity and a wider CL spectral linewidth can be obtained at the edge of the central disk. In order to further improve the focusing ability, a cylindrical Pt nanostructure has been deposited on the central disk. Additionally, the finite element simulation indicates that the electric-field enhancement originates from the coupling process between the plasmonic emission from the Bi2Te3 bullseye and the Pt nanostructure. Finally, we find that enhancement efficiency depends on the thickness of the Pt nanostructure.
The defects into the hexagonal network of a sp
2
-hybridized carbon atom have been demonstrated to have a significant influence on intrinsic properties of graphene systems. In this paper, we ...presented a study of temperature-dependent Raman spectra of G peak and D’ band at low temperatures from 78 to 318 K in defective monolayer to few-layer graphene induced by ion C+ bombardment under the determination of vacancy uniformity. Defects lead to the increase of the negative temperature coefficient of G peak, with a value almost identical to that of D’ band. However, the variation of frequency and linewidth of G peak with layer number is contrary to D’ band. It derives from the related electron-phonon interaction in G and D’ phonon in the disorder-induced Raman scattering process. Our results are helpful to understand the mechanism of temperature-dependent phonons in graphene-based materials and provide valuable information on thermal properties of defects for the application of graphene-based devices.
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