Nanourchin-shaped narrow-band-gap semiconductor photocatalysts with high surface area combined with good crystallinity result in effective photocatalysis. In this work, the impregnating growth of 1D CdS nanowires onto Al 2 O 3 and ZnO templates as cores generates novel urchinlike morphology of CdS@oxide photocatalysts. The CdS@Al 2 O 3 and CdS@ZnO nanourchins explicitly show a major role in enhanced hydrogen generation with apparent quantum yields (AQY) of 11% and 15%, respectively. Mechanistically, the template-based CdS can influence the photocatalytic activity in two ways: (i) direct well-dispersed growth of CdS onto the oxide core, leading to a high surface area for enhanced light absorption, and (ii) charge transfer from the conduction band of highly crystalline CdS to that of the oxide, which facilitate efficient charge separation for hydrogen production. Following these two mechanisms, a simple, low-cost, and environmentally friendly hydrothermal strategy is employed to synthesize novel nanourchin-shaped CdS-based heteroarrays. This new morphology stimulates the surface area per unit volume of the photocatalyst and exhibits promising application for photocatalytic water splitting.
Hydrothermally grown one-dimensional ZnO nanowire (1D ZnO NW) and a newly synthesized metal-free, D-π-A type, carbazole dye (SK1) sensitizer-based photovoltaic device with a power conversion efficiency (PCE) of more than 5% have been demonstrated by employing the cobalt tris(2,2'-bipyridyl) redox shuttle. A short-circuit current density (Jsc) of ∼12.0 mA/cm(2), an open-circuit voltage (Voc) of ∼719 mV, and a fill factor (FF) of ∼65% have been afforded by the 1D ZnO NW-based dye-sensitized solar cell (DSSC) incorporating [Co(bpy)3](3+/2+) complex as the one-electron redox mediator. In contrast, the identical DSSC with traditional I3(-)/I(-) electrolyte has shown a Jsc ≈ 12.2 mA/cm(2), a Voc ≈ 629 mV, and a FF ≈ 62%, yielding a PCE of ∼4.7%. The persuasive role of the inherent superior electron transport property of 1D ZnO NWs in enhancing the device efficiency is evidenced from the impoverished performance of the DSSCs with photoanodes fabricated using ZnO nanoparticles (NPs). The DSSCs having ZnO NP-based photoanodes have achieved the PCEs of ∼3.6% and ∼3.2% using cobalt- and iodine-based redox electrolytes, respectively. The electronic interactions between the SK1 sensitizer and ZnO (NWs and NPs) to induce the photogenerated charge transfer from SK1 to the conduction band (CB) of ZnO are evidenced from the significant quenching of photoluminescence and exciton lifetime decay of SK1, when it is anchored onto the ZnO architectures. The energetics of the SK1 dye molecule are estimated by combining the spectroscopic and electrochemical techniques. The electronic distributions of SK1 dye molecule in its HOMO and LUMO energy levels are interpreted using density functional theory (DFT)-based calculations. The electron donor-π linker-acceptor (D-π-A) configuration of SK1 dye provides an intramolecular charge transfer within the molecule, prompting the electron migration from the carbazole donor to cyanoacrylic acceptor moiety via the oligo-phenylenevinylene linker group. The D-π-A-mediated electron movement witnesses the favorable photoexcited electron transfer from the LUMO of SK1 dye to the CB of ZnO through the carboxyl anchoring group.
We report, for the first time, a ternary hybrid composite of ZnO, CdS, and graphene oxide (GO) as a one-coat paintable solution in performing the role of a photoanode for the semiconductor-sensitized solar cell, wherein hierarchical ZnO− CdS heteroarrays are embedded onto the GO sheets. The photoconversion properties of the hybrid ternary-system-based photoanodes are evaluated in the photovoltaic devices having Pt and Ag as the counter electrodes with sulfide/polysulfide redox couple as the electrolyte. Power conversion efficiency (PCE) of ∼2.82% has been achieved with a short-circuit current density (J sc ) of ∼7.3 mA/cm 2 , a maximum open-circuit voltage (V oc ) of 703 mV, and a fill factor (FF) of 54% for the photovoltaic cell with Pt as a counter electrode. The identical hybrid photoanode against the Ag counter electrode resulted in the following values: PCE ≈ 1.96%, J sc ≈ 5.7 mA/cm 2 , V oc ≈ 565 mV, and 63% FF. The band position proximity of CdS, ZnO, and GO in the proposed ternary system facilitates an efficient electronic interactions thereby promoting the electron transport within CdS− ZnO−GO. The hierarchically grown CdS nanorods over ZnO nanoparticle act as the sensitizer for ZnO, enhancing the visible light harvesting ability. The loading of 1.0 wt % of GO to ZnO−CdS results in enhanced separation of photogenerated electrons and holes within the photoactive layer, thereby improving the photovoltaic performance. The electronic interactions of GO to ZnO−CdS is evident from the drastic quenching of fluorescence, reduced exciton lifetime and Raman scattering measurements. In order to study the effect of GO in the photovoltaic performance, we have compared our result with the photoelectrical parameters of the devices fabricated using the binary ZnO−CdS composite as GO-free photoanodes.
Polymerizing
monomers on an atomically flat solid surface and air/water,
solid/liquid, or liquid/liquid interface is now a rapidly emerging
frontier. Dimension-controlled synthesis of π-conjugated polymers
is of particular interest, which can be achieved by precise control
of monomer distribution during the polymerization. The surface of
ice allows rapid polymerization of monomers in the plane direction
along the air–water interface to yield large-area two-dimensional
sheet-like poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)
(2D sheet-like PEDOT:PSS) films with a thickness of ca. 30 nm. The persuasive role of ice chemistry is reflected in the
high degree of crystallinity and superior conductivity of resultant
PEDOT:PSS films. Excellent photoelectrochemical features were further
disclosed when the ice-templated PEDOT:PSS films were coupled to quantum
dots. Utilization of these polymer films in photovoltaic devices also
resulted in excellent current density and power conversion efficiency.
This work presents an innovative material technology that goes beyond
traditional and ubiquitous inorganic 2D materials such as graphene
and MoS2 for integrated electronic applications.
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