Silicon nanostructure-based solar cells have lately intrigued intensive interest because of their promising potential in next-generation solar energy conversion devices. Herein, we report a silicon ...nanowire (SiNW) array/carbon quantum dot (CQD) core–shell heterojunction photovoltaic device by directly coating Ag-assisted chemical-etched SiNW arrays with CQDs. The heterojunction with a barrier height of 0.75 eV exhibited excellent rectifying behavior with a rectification ratio of 103 at ±0.8 V in the dark and power conversion efficiency (PCE) as high as 9.10% under AM 1.5G irradiation. It is believed that such a high PCE comes from the improved optical absorption as well as the optimized carrier transfer and collection capability. Furthermore, the heterojunction could function as a high-performance self-driven visible light photodetector operating in a wide switching wavelength with good stability, high sensitivity, and fast response speed. It is expected that the present SiNW array/CQD core–shell heterojunction device could find potential applications in future high-performance optoelectronic devices.
This paper presents a systematic investigation on the incorporation of chemical exfoliation graphene sheets (GS) in TiO2 nanoparticle films via a molecular grafting method for dye-sensitized solar ...cells (DSSCs). By controlling the oxidation time in the chemical exfoliation process, both high conductivity of reduced GS and good attachment of TiO2 nanoparticles on the GS were achieved. Uniform GS/TiO2 composite films with large areas on conductive glass were prepared by electrophoretic deposition, and the incorporation of GS significantly improved the conductivity of the TiO2 nanoparticle film by more than 2 orders of magnitude. Moreover, the power conversion efficiency for DSSC based on GS/TiO2 composite films is more than 5 times higher than that based on TiO2 alone, indicating that the incorporation of GS is an efficient means for enhancing the photovoltaic (PV) performance. The better PV performance of GS/TiO2 DSSC is also attributed to the better dye loading of GS/TiO2 film than that of TiO2 film. The effect of GS content on the PV performances was also investigated. It was found that the power conversion efficiency increased first and then decreased with the increasing of GS concentration due to the decrease in the transmittance at high GS content. Further improvements can be expected by fully optimizing fabrication conditions and device configuration, such as increasing dye loading via thicker films. The present synthetic strategy is expected to lead to a family of composites with designed properties.
Well-aligned ZnO nanoneedle and nanorod arrays were grown on an aluminum-doped zinc oxide (AZO) buffer layer by chemical vapor deposition and used as templates for making gold-coated ZnO (ZnO/Au) ...composite nanoarrays. The coverage of Au nanoparticles on ZnO nanoneedle and nanorod was controlled by varying the concentration of Au precursor. High coverage led to the formation of ZnO/Au nanoneedle bundles. The ZnO/Au composite nanoarrays were applied as substrates in surface-enhanced Raman scattering (SERS) measurement. The SERS enhancement factor is mainly controlled by gold coverage and morphologies of the ZnO/Au nanoarrays. Their application in rapid detection of melamine in egg white is demonstrated. This SERS-based melamine detection is advantageous in that sample pretreatment is not needed. It showed the potential of the ZnO/Au nanoarrays as a convenient and robust SERS-active substrate for food safety monitoring.
The photoconductivity of a methyl squarylium (MeSq) single‐nanowire device shows a high light sensitivity, wavelength‐dependent photoresponse, good response speed, and excellent stability and ...reproducibility. Nanodevices fabricated on flexible substrates (see figure) exhibit good mechanical bendability and no obvious change in performance after bending to a curvature of 0.5 cm−1.
We present the first report of a new suspension method for obtaining cubic MAPbBr3 single crystal with a concave surface. The cubic MAPbBr3 crystal with microconcavity possesses good crystallinity ...and carrier lifetime. Excellent photoelectric performance was provided by the concavity-based MAPbBr3 photodetectors because of the good light trapping and shortened carrier pathway. As a result, the concavity-based photodetector exhibits superior responsivity of 62.9 and 5.43 A W–1 and EQE of 1.50 × 104% and 1.30 × 103% under low-power and high-power 520 nm irradiation of 3.67 μW cm–2 and 35.4 mW cm–2 at 3 V, respectively, which are more than 500% higher than those of the plane-based photodetector. In particular, the concavity-based photodetector has an ultrahigh detectivity of 6.5 × 1012 Jones at ultralow power of 3.67 μW cm–2, which is 6.5 times higher than that of the planar device.
► ZnO nanoparticles and nanorods array grew simultaneously on both surfaces of a silicon substrate. ► The growth of two structures was controlled by the deposition rate of Zn atoms. ►Two ZnO ...structures have opposite relative intensities of UV emission to visible emission. ►Their wetting behavior changed with the evaporation of water droplets.
By controlling the deposition rate of Zn atoms, we simultaneously synthesized ZnO particles on the upper surface of a horizontal silicon substrate, and ZnO rods array on its lower surface via a thermal evaporation process. The deposition rate of Zn atoms not only affects the morphologies of the final ZnO products, but also consequently leads to ZnO particles and ZnO rods array that have different photoluminescence properties and wetting behaviors. These two morphological ZnO products have just opposite relative intensities of UV emission to visible emission. ZnO rods array has a water contact angle of 160.3°, while ZnO particles film has a water contact angle of 150.4°, and their wetting behavior changed from the Cassie state to the Wenzel state during the process of droplet evaporation.
In this paper, the role of fullerene loading on the nanomorphology and photovoltaic performance of alternating copolymer poly{2-octyldodecyloxy-benzo1,2-b;3,4-b ...dithiophene-alt-5,6-bis(dodecyloxy)-4,7bis(thiophen-2-yl)-benzoc 1,2,5-thiadiazole} (PBDT-ABT-1) blend films was investigated. The morphology of blend films with different Phenyl C-60-butyric acid methyl ester (PCBM) mixing ratios and solvent additives was studied using atomic force microscopy (AFM) and energy-filtered transmission electron microscopy (EFTEM). AFM and EFTEM images showed difference in the intermixing of polymer with fullerene between 1:1, 1:2, and 1:3 weight ratios. Polymer/PCBM intermixed domain size increases with higher PCBM weight ratios. X-ray diffraction measurements on the pristine polymer and blend films cast without additives did not show any peaks, suggesting an amorphous nature of PBDT-ABT-1. EFTEM images from the donor/acceptor composite showed intermixed polymer-PCBM domains separated by the polymer boundary. Furthermore, EFTEM images for di-iodooctane (DIO) additive cast film revealed purer polymer domain. Photo-charge extraction by linearly increasing voltage measurement exhibited that charge extraction is highest in the nanomorphology sample with a weight ratio of 1:2, corresponding to the lowest bimolecular recombination and the highest charge carrier mobility.
n‐Type doping of CdSe nanowires is achieved by either co‐evaporating indium at different temperatures during growth, or post‐growth doping via a thermal diffusion process. The conductivity of CdSe ...nanowires is tuned reproducibly by nearly five orders of magnitude in a controlled way, and carrier concentration as high as ∼1019 cm−3 is reached (see image). The doped CdSe nanowires show high sensitivity to light irradiation.
