Jianping Deng

CdS and CdSe quantum dots subsectionally sensitized solar cells using a novel double-layer ZnO nanorod arrays

We report a novel approach for synthesizing CdS and CdSe quantum dots subsectionally sensitized double-layer ZnO nanorods for solar cells, which are comprised of CdS QDs-sensitized bottom-layer ZnO NRs and CdSe QDs-sensitized top-layer ZnO NRs. X-ray diffraction study and scanning electron microscopy analysis indicate that the solar cells of subsectionally sensitized double-layer ZnO NRs, which are the hexagonal wurtzite crystal structure, have been successfully achieved. The novel structure enlarged the range of absorbed light and enhanced the absorption intensity of light. The I-V characteristics show that the double-layer structure improved both the current density (J(sc)) and fill factor (FF) by 50%, respectively, and power conversion efficiency (η) was increased to twice in comparison with the CdS QDs-sensitized structure.

One-Step Preparation and Assembly of Aqueous Colloidal CdSxSe1–x Nanocrystals within Mesoporous TiO2 Films for Quantum Dot-Sensitized Solar Cells

In the field of quantum dots (QDs)-sensitized solar cells, semiconductor QDs sensitizer with a moderate band gap is required in order to sufficiently match the solar spectrum and achieve efficient charge separation. At present, changing the size of QDs is the main method used for adjusting their band gap through quantum size effect, however, the pore sizes of mesoporous TiO2 film set a limit on the allowed size of QDs. Therefore, the tuning of electronic and optical properties by changing the particle size could be limited under some circumstances. In this paper, high-quality aqueous CdS(x)Se(1-x) QDs sensitizer is successfully synthesized and effectively deposited on a mesoporous TiO2 film by a one-step hydrothermal method. In addition to size, alloy QDs provide composition as an additional dimension for tailoring their electronic properties. The alloy composition and band gap can be precisely controlled by tuning the precursor (Se/Na2S·9H2O) ratio while maintaining the similar particle size. By using such CdS(x)Se(1-x) sensitized TiO2 films as photoanodes for solar cell, a maximum power conversion efficiency of 2.23% is achieved under one sun illumination (AM 1.5 G, 100 mW cm(-2)).

Arrays of ZnO/AZO (Al-doped ZnO) nanocables: a higher open circuit voltage and remarkable improvement of efficiency for CdS-sensitized solar cells.

Photoelectrode of nanocables (NCs) structure of ZnO nanowires (NWs) coated with Al-doped ZnO (AZO) shells was investigated for CdS quantum dots sensitized solar cells (QDSSCs). ZnO NWs serve as the frame for the preparation of AZO shells, in which electron transport more rapidly due to the more higher electron mobility of AZO (n-ZnO) than that of i-ZnO. AZO shells were assembled onto the surface of ZnO NWs via a spin-coating method. Optical band-gap of the ZnO/AZO films varies from 3.19 eV for pure ZnO to 3.25 eV for AZO (15%) depending on the Al-doping concentration. The PL intensity of AZO/ZnO, V(oc), J(sc) and η of the cells first increased and then decreased with the increase in the Al-doping (from 0% to 20%) and post-annealed temperature. Remarkably, the value of V(oc) can achieve above 0.8 V after Al-doping. The dark current and absorption spectrum provided direct evidence of the increase in J(sc) and V(oc), respectively. Moreover, we discussed the effect of Al-doping on optical band-gap of the samples and the transfer of electron.

Employing the plasmonic effect of the Ag–graphene composite for enhancing light harvesting and photoluminescence quenching efficiency of poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene-vinylene]

In this work, we report that the Ag-graphene composite (AGC) can effectively enhance the light harvesting and photoluminescence (PL) quenching efficiency of poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene-vinylene] (MEH-PPV). Loading the AGC on MEH-PPV leads to improved light absorption ability and PL quenching efficiency, which is due to the strong interaction between localized surface plasmon resonance (LSPR)-activated Ag nanoparticles and the MEH-PPV molecule. Control experiment reveals that the combination of graphene and Ag nanoparticles achieves superior light absorptivity and PL quenching ability compared with individual graphene and Ag NPs. The exponential shape of the Stern-Volmer plot implies that both Ag and graphene in the AGC can offer the quenching pathway for the PL quenching process. We also found that the AGC with a broader LSPR absorption range is competitive in enhancing the light absorption ability and PL quenching efficiency of the MEH-PPV-AGC composite, because it can expand LSPR-induced light harvesting and PL quenching response to a wider absorption range.

A general route to enhance the fluorescence of graphene quantum dots by Ag nanoparticles

Graphene quantum dots (GQDs)/Ag nanoparticles with an unexpected quantum yield of 16.3% are synthesized by an efficient simple solvothermal method at atmospheric pressure. Experimental results show that the enhanced fluorescence is caused by the plasmonic effect of the Ag nanoparticles. The possible mechanism of this fluorescence enhancement is also proposed.

TiO2 nanoparticle/ZnO nanowire hybrid photoanode for enhanced quantum dot-sensitized solar cell performance

A hybrid structured TiO2/ZnO photoanode was composed of highly ordered ZnO nanowires (NWs) and small TiO2 nanoparticles (NPs) filling the gaps among ZnO NWs. In this way, ZnO NWs provide a direct pathway to facilitate electron collection and transport and increase light scattering and trapping. TiO2 NPs provide a large specific surface to effectively adsorb quantum dots (QDs). In experiments, the density of ZnO NW arrays was first controlled by regulating the ratio of TiO2 NPs to ZnO NPs and the concentration of ZnO NPs in the hybrid NP seed precursor, and then the TiO2 paste was successfully use to fill the gaps among NWs by a large centrifugal force. Using TiO2 NP/ZnO NW films as photoanodes, we fabricated CdSe QD-sensitized solar cells and tested their photovoltaic (PV) performances. The results demonstrated a remarkably enhanced short-circuit current density (Jsc) of 7.9 mA cm−2 and power conversion efficiency (η) of 1.55%, and this η is enhanced by 19.2% and 30.3%, respectively, compared to those of a TiO2 NP device with an η of 1.3% and a ZnO NW device with an η of 1.19%.

Engineering the plasmonic optical properties of cubic silver nanostructures based on Fano resonance.

The plasmonic optical properties of nanostructures including a dimer, a linear chain, a T-shaped nanostructure, and a 2D array consisting of Ag nanocubes have been investigated using the discrete dipole approximation method. The simulation results indicate that both the interparticle gap and polarization have an important impact on far-field and near-field characteristics. With decreasing interparticle distance for four nanostructures, the plasmon resonance peak is monotonically red-shifted and the electric intensity enhancement factor increases rapidly due to increased interparticle coupling interaction. Moreover, we also find that a T-shaped nanostructure has the largest electric intensity enhancement factor compared with other three nanostructures due to the coupling interaction at the intersection. This coupling is caused by the radiative interference between subradiant and superradiant resulting in Fano resonance. These results show how nanostructure arrangement design, gap adjustment, and polarization control can be used to achieve high field enhancements.

The influence of blocking layer on the photovoltaic performance of organometal halide perovskite solar cell

The existence of a compact electron blocking layer is critical in organometal halide perovskite solar cell, since it prevented the charge recombination originated in fluorine-doped tin oxide (FTO) electrode and the hole conducting layer and ensured an effective charge abstract. A compact TiO2 thin film was fabricated on FTO by spin coating different sols. Commercial peroxo titanic acid (PTA) aqueous sol and titanium isopropoxide (TTIP) sol prepared according to literature were used to regulate the performance of the compact layer. With the optimized blocking layer a PCE of 5.15% was archived with P3HT as hole-transport material (HTM) and magnetron sputtering Ag as counter electrode.

One-pot synthesis of stabilizer-free Ag-Graphene Nanocomposite and its potential application on photodegradation of RhB

Simultaneous reduction of graphene oxide (GO) and silver nitrate (AgNO3) into stabilizer-free Ag-Graphene Naoncomposite (AGN) using DMAc-assisted thermal reduction method with controllable density of Ag nanoparticles (Ag NPs) is reported. Microscopy techniques (scanning electron microscopy and high-resolution transmission electron microscopy) have been employed to probe the morphological characteristics of AGN and the lattice plane of Ag NPs. We observed a significant improvement on adsorption ability of AGN-P25 mixture compared with bare P25, indicating potential application on photocatalysis of AGN.