The enhancement of power conversion efficiency (PCE) and the development of toxic Cd-, Pb-free quantum dots (QDs) are critical for the prosperity of QD-based solar cells. It is known that the properties (such as light harvesting range, band gap alignment, density of trap state defects, etc.) of QD light harvesters play a crucial effect on the photovoltaic performance of QD based solar cells. Herein, high quality ∼4 nm Cd-, Pb-free Zn-Cu-In-Se alloyed QDs with an absorption onset extending to ∼1000 nm were developed as effective light harvesters to construct quantum dot sensitized solar cells (QDSCs). Due to the small particle size, the developed QD sensitizer can be efficiently immobilized on TiO2 film electrode in less than 0.5 h. An average PCE of 11.66% and a certified PCE of 11.61% have been demonstrated in the QDSCs based on these Zn-Cu-In-Se QDs. The remarkably improved photovoltaic performance for Zn-Cu-In-Se QDSCs vs Cu-In-Se QDSCs (11.66% vs 9.54% in PCE) is mainly derived from the higher conduction band edge, which favors the photogenerated electron extraction and results in higher photocurrent, and the alloyed structure of Zn-Cu-In-Se QD light harvester, which benefits the suppression of charge recombination at photoanode/electrolyte interfaces and thus improves the photovoltage.
We develop a general framework of evaluating the Stimulated Brillouin Scattering (SBS) gain coefficient in optical waveguides via the overlap integral between optical and elastic eigen-modes. This full-vectorial formulation of SBS coupling rigorously accounts for the effects of both radiation pressure and electrostriction within micro- and nano-scale waveguides. We show that both contributions play a critical role in SBS coupling as modal confinement approaches the sub-wavelength scale. Through analysis of each contribution to the optical force, we show that spatial symmetry of the optical force dictates the selection rules of the excitable elastic modes. By applying this method to a rectangular silicon waveguide, we demonstrate how the optical force distribution and elastic modal profiles jointly determine the magnitude and scaling of SBS gains in both forward and backward SBS processes. We further apply this method to the study of intra- and inter-modal SBS processes, and demonstrate that the coupling between distinct optical modes are necessary to excite elastic modes with all possible symmetries. For example, we show that strong inter-polarization coupling can be achieved between the fundamental TE- and TM-like modes of a suspended silicon waveguide.
Flexible and transparent power sources are highly desirable in realizing next-generation all-in-one bendable, implantable, and wearable electronic systems. The developed power sources are either flexible but opaque or semitransparent but lack of flexibility. Therefore, there is increasing recognition of the need for a new concept of electrochemical device structure design that allows both high flexibility and transparency. In this paper, we present a new concept for electrochemical device design--a two-dimensional planar comb-teeth architecture on PET substrate--to achieve both high mechanical flexibility and light transparency. Two types of prototypes--dye-sensitized solar cells and supercapacitors--have been fabricated as planar devices and demonstrated excellent device performance, such as good light transparency, excellent flexibility, outstanding multiple large bending tolerance, light weight, effective prevention of short circuits during bending, and high device integration with up-date microelectronics, compared to conventional sandwich structure devices. Our planar design provides an attractive strategy toward the development of flexible, semitransparent electrochemical devices for fully all-in-one elegant and wearable energy management.
Ab iosensor was created for the simultaneous monitoring of endogenous H 2 S n and H 2 Si nm ouse brains and exploring their roles in activation of the TRPA1 channel under two types of brain disease models:i schemia and Alzheimersd isease (AD). Based on DFT calculations and electrochemical measurements,t wo probes,3 ,4-bis((2-fluoro-5-nitrobenzoyl)oxy)-benzoic acid (M PS-1 )a nd N-(4-(2,5-dinitrophenoxy) phenyl)-5-(1, 2-dithiolan-3-yl)pentanamide (M HS-1 ), were synthesized for specific recognition of H 2 S n and H 2 S. Through co-assembly of the two probes at the mesoporous gold film with good anti-biofouling ability and electrocatalytic activity,this microsensor showed high selectivity for H 2 S n and H 2 Sa gainst potential biological interferences.T he biosensor can simultaneously determine the concentration of H 2 S n from 0.2 to 50 mm,a sw ell as that of H 2 Sf rom 0.2 to 40 mm.T he expression of TRPA1 protein positively correlated with levels of H 2 S n under both ischemiaa nd AD.
Monodisperse TiO 2 hollow spheres assembled by nanospindles were prepared via the facile hydrothermal reaction of peroxotitanium complex precursors. Time dependent trails revealed that the shape evolution involved a one-step chemical conversion from amorphous Ti complex microspheres to anatase TiO 2 hierarchical hollow spheres. Meanwhile, the sizes of the spheres could be tuned in a region of 400-1000 nm by simply adjusting the ammonia dosage of the precursor solution. Furthermore, these as-prepared hollow spheres were deposited as a scattering layer on top of the TiO 2 nanocrystalline film, and a high energy conversion efficiency of 8.10% was demonstrated based on the bilayer photoanode, in contrast to a 7.29% conversion efficiency for the cell with a pure nanocrystalline photoanode.
An ideal counter electrode, with high electrocatalytic activity, high performance stability, and applicable fabrication simplicity, is essential to give full play to the advantages of quantum-dot-sensitized solar cells (QDSSCs) such as high theoretical efficiency and simple synthetic procedure. Herein, we report a facile one-step electrochemical deposition approach for the growth of hierarchical covellite (CuS) nanostructures on conductive glass substrates. The as-synthesized copper sulfide can be employed directly as a robust, low-cost, and high-efficiency counter electrode without any post-treatments for QDSSCs filled with aqueous sulfide/polysulfide (S 2− /S n 2− ) electrolyte. The morphology and structure of the well-crystalline, strongly substrate-adhesive hierarchical CuS nanostructured film have been studied by X-ray and electron-based characterizations. QDSSC using this newly synthesized CuS as counter electrode achieves a higher power conversion efficiency of 4.32% than the one applying cuprous sulfide (Cu 2 S) on brass substrate (4.08%) or platinum counter electrode (2.85%). Furthermore, this CuS counter electrode shows a high and consistent electrocatalytic activity toward polysulfide reduction confirmed by the electrochemical measurements, destining the improved photovoltaic performance and superior stability of the corresponding QDSSC device.
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