• Energy Research

Abstract Al 2 O 3 -coated TiO 2 porous films were used to fabricate solid-state dye-sensitized solar cells using CuI as hole conductor. Investigation with transient photovoltage measurements showed that the Al 2 O 3 interlayer slowed down the interfacial recombination of electrons in TiO 2 with holes in CuI by forming a potential barrier at the TiO 2 /CuI interface. As a consequence, the cell made from Al 2 O 3 -coated TiO 2 film showed superior cell performance than the cell made from TiO 2 film only, especially under relative high intensity of simulated sunlight.

Abstract PbS colloidal quantum dot solar cells (CQDSCs) employ ZnO electron transport layer have achieved high efficiency. However, there is nearly no efficient and batch production method to balance the charge separation and recombination within the device, which is one of the most obviously barrier to a satisfactory conversion efficiency. Here, a n+-n double-layered ZnO electron transport layer (DETL) is prepared by a facile one-step magnetron sputtering under different Ar pressure, and employed in heterojunction PbS colloidal quantum dot solar cells (CQDSCs) for the purpose of increasing charge separation at heterojunction interface via energy-band alignment modulation. The ZnO DETL, composed of a 100-nm-thick n+-ZnO bottom layer (n = 8 × 1019 cm−3) and a 20-nm-thick n-ZnO top layer (n = 3 × 1016 cm−3) significantly improve the power conversion efficiency (PCE) of the CQDSCs by a factor of ~35% compared to the device with single-layered n- ZnO. Open-circuit photovoltage decay (OCVD) measurements prove that the graded energy alignment of ZnO DETL effectively reduces both interfacial and trapping-assisted charge recombination, relative to the single-layered ZnO. The facile Ar-pressure tuning method makes the energy-band alignment process more convenient and sheds a light on the application of DETL electrons transport layer, fabricated by the universal technique of magnetron sputtering.

Cyclic voltammetry was used in order to directly deposit hydrous ruthenium oxide (RuO x ·nH 2 O) on conductive diamond substrates. It was found that, at the hydrogen-terminated boron-doped diamond (BDD) surface, the overall deposition process is rather slow compared to the case of metal substrates. Nevertheless, the values estimated for the specific charge and specific capacitance by cyclic voltammetric and chronopotentiometric experiments, respectively, compare favorably to those reported in the literature. Additional advantages of using a BDD support are the excellent stability of the response, the extreme robustness even under severe functioning conditions, and, importantly, negligible substrate effects. It was also observed that RuO x ·nH 2 O deposition at a BDD powder surface greatly enhanced both the specific charge and the specific capacitance. These features strongly recommend the use of conductive diamond powder as a substrate for hydrous ruthenium oxide, particularly in view of possible, electrochemical capacitor applications.

Abstract The perovskite structure BaSnO3 is regarded as a promising photoanode material, and an effective necking treatment strategy is necessary for the electrical connectivity of mesoporous BaSnO3 photoanode-based solar cells. The often-adopted necking strategy involves the treatment in TiCl4 solution with low pH, which can lead to the leaching of barium cations from BaSnO3 and impair the effect of the necking treatment. To address this issue, we report herein a novel noncorrosive necking strategy based on the common ion effect. The strategy involved treating the mesoporous BaSnO3 photoanode with a mixture solution of TiCl4 and BaCl2. Compared with the common TiCl4 necking treatment, the treatment with TiCl4 and BaCl2 mixture solution negligibly affected the formation of the TiO2 overlayer on the surface of BaSnO3 particles, but it maintained the crystallinity of the BaSnO3 particles. The TiCl4 and BaCl2 mixture solution treated BaSnO3 photoanodes were assembled into CdSe/CdS co-sensitized quantum dot-sensitized solar cells (QDSSCs), which showed ca. 37% increase in power conversion efficiency in comparison with the TiCl4 treated photoanode. The charge extraction, electrochemical impedance spectroscopy, and intensity-modulated voltage/photocurrent spectroscopy measurements showed that the QDSSCs fabricated from the TiCl4 and BaCl2 mixture solution treated BaSnO3 photoanode contained fewer trap states and exhibited less charge recombination and longer electron lifetime than those based on the common TiCl4 treated photoanodes, demonstrating the effectiveness of the noncorrosive necking treatment.

Abstract Ion doping strategy is a promising method to enhance the efficiency of Cu2ZnSn(S,Se)4 (CZTSSe) solar cells, however, most of the reported works focus on studying the single ion doping in CZTSSe absorber layers. Here, Li+&Ag+ and Li+&Cd2+ double-ion-doping strategy are applied to improve the microstructure and device performances. We found that the double-ion-doping strategy can obviously increase the grain size, reduce the thickness of fine-grain layers and enhance the device performances. Furthermore, the PCEs of Li+&Ag+ and Li+&Cd2+ doped CZTSSe solar cells are up to 8.87% and 8.39%, respectively. It shows an encouraging improvement of over 43.5% and 35.8% enhancement compared with the traditional method (6.18%), and significantly higher than single ion doping strategy (7.60%, 7.99% and 7.11% for Li+, Ag+, and Cd2+ doped CZTSSe solar cells). This work provides a new solution to improve the microstructure and device performances of CZTSSe solar cells.

Abstract This paper reports the preparation of a core-shell nanoporous electrode consisting of an inner TiO2 porous matrix and a thin overlayer of Al2O3, and its application for solid-state dye-sensitized solar cell using p-CuI as hole conductor. Al2O3 overlayer was coated onto TiO2 porous film by the surface sol–gel process. The role of Al2O3 layer thickness on the cell performance was investigated. The solar cells fabricated from Al2O3-coated electrodes showed superior performance to the bare TiO2 electrode. Under illumination of AM 1.5 simulated sunlight (89 mW/cm2), a ca. 0.19 nm Al2O3 overlayer increased the photo-to-electric conversion efficiency from 1.94% to 2.59%.

Abstract In this work, the ZnO/Cu2−xS composite material is prepared based on Al doped zinc oxide glass substrate and applied as counter electrode (CE) in quantum dot sensitized solar cell. The ZnO/Cu2−xS CEs with the different Cu/S ratios of Cu2−xS (2-x = 1.73–1.48) can be controlled by immersing Cu/ZnO in different concentrations of S2- solution. As a result, the solar cell fabricated by Cu1.62S/ZnO CE exhibits the best photoelectric conversion efficiency of 5.35% under 1 sun illumination, which is higher than that of Cu1.62S CE (4.22%). On the basis of the result of solid-state current density–voltage test and transient photovoltage measurements, the formation of p-n heterojunction and the improving electrocatalytic activity in composite CEs accounts for the enhanced photoelectric conversion efficiency. These results are coincide with the outcomes of the impedance analysis, Tafel polarization measurement and cyclic voltammetry test for the symmetrical cell. Consequentially, the ZnO/Cu2−xS composite counter electrode is a promising material and the applications in solar cells.

Abstract We report here that a facile sol–gel dip-coating technique can be used to fabricate a SiO2/TiO2 bilayer film with self-cleaning and antireflection properties. The bottom SiO2 layer acts as an antireflection coating due to its lower refractive index; the top TiO2 layer acts as a self-cleaning coating generated from its photocatalysis and photo-induced superhydrophilicity. The maximal transmittance of SiO2/TiO2 bilayer film at normally incident light can be reached 96.7%, independent of the high refractive index and coverage of TiO2 nanoparticles. However, the photocatalytic activity of the bilayer film shows a close dependence on coverage of TiO2 nanoparticles. After illuminated by ultraviolet light, the SiO2/TiO2 bilayer films are superhydrophilic with water contact angle less than 2°, which favors greatly the self-cleaning function of the films.

New zinc phthalocyanine (ZnPc-TDA), peripherally functionalized with donor-acceptor conjugates was synthesized, and its optical, thermal, electrochemical, and photovoltaic properties were studied. The black ZnPc-TDA exhibited both excellent solubility in common organic solvents, and broad absorption covering the range 300-900 nm. The photovoltaic devices with the configuration of ITO/PEDOT-PSS/ZnPc-TDA:PCBM/LiF/Al produced short circuit current densities of 2.26 mA/cm(2), the open circuit voltage of 0.68 V and power conversion efficiency of 0.4% under AM1.5G illumination. (C) 2010 Elsevier B.V. All rights reserved.