ZnSxSe1-x Alloy Passivation Layer for High-Efficiency Quantum-Dot-Sensitized Solar Cells

Dispersible CdS1-xSex solid-solution nanocrystal photocatalysts: Photoinduced self-transformation synthesis and enhanced hydrogen-evolution activity

Modulating the electronic structure of Cadmium sulfide (CdS) by non-metallic elements to produce solid-solution photocatalysts serves as a potential route to improve its performance of photocatalytic hydrogen (H₂) evolution. However, exploring an effective synthetic route of CdS-based solid solution is still a great challenge. Herein, the CdS_1-xSe_x solid-solution nanocrystals were successfully synthesized by an accessible photoinduced self-transformation route, including the direct formation of dispersible CdS_1-x(SeS)_x and the in situ self-transformation of selenosulfide ((SeS)^2-) to Se^2- by photoexcited electrons. The prepared CdS_1-xSe_x solid-solution photocatalysts possess a small crystallite size of ca. 5 nm and their bandgaps can be easily tuned in a wide range of 1.84-2.28 eV by tailoring the mole ratio of Se/S. The resultant CdS_0.90Se_0.10 solid-solution photocatalyst realizes the highest H₂-production tempo of 94.6 μmol·h^-1, which is 1.6 folds higher than that of CdS. The experimental and theoretical studies supported that the incorporation of Se atoms could not only narrow the bandgap value to reinforce visible-light absorption, but also tune its electronic structure to optimize interfacial H₂-evolution dynamics, thus achieving an efficient photocatalytic H₂-production rate of the dispersible CdS_1-xSe_x solid solution. This study may deliver advanced inspirations for optimizing the electronic structure of photocatalysts towards sustainable H₂ production.

In situ sulfidation of porous sponge-like CuO/SiW11Co into Cu2S/SiW11Co as stabilized and efficient counter electrode for quantum dot-sensitized solar cells

Quantum dot-sensitized solar cells (QDSSCs), which are cost-effective, facilely prepared and environmentally friendly, are regarded as a promising third-generation photovoltaic technology, although the conversion efficiency of QDSSCs is still far lower than the theoretical efficiency (44%). Furthermore, the traditional Cu₂S/brass counter electrode (CE) is susceptible to continuous corrosion from the polysulfide electrolyte, reducing the stability and electrocatalytic activity of the CE, thereby affecting cell performance. To enhance the stability of the Cu₂S CE and make full use of its excellent catalytic properties, we used eco-friendly polyoxometalates (K₆SiW₁₁O₃₉Co(ii) (H₂O), SiW₁₁Co) and porous sponge-like CuO as precursors to prepare a novel SiW₁₁Co-doped high-efficiency Cu₂S/SiW₁₁Co CE on FTO by adopting the method of in situ sulfidation in the electrolyte. Electrochemical analysis revealed that the novel Cu₂S/2%-SiW₁₁Co (Cu₂S-2) CE exhibits extremely high stability and electrocatalytic performance compared with other electrodes. Meanwhile, adding an appropriate amount of SiW₁₁Co can inhibit charge recombination and improve cell performance. The CdS/CdSe co-sensitized QDSSCs assembled with the novel Cu₂S-2 CE obtained a power conversion efficiency (PCE) of 5.94%, which was 20% more efficient than QDSSCs based on Cu₂S/brass CE (4.96%). The method reported here puts forth a new direction for the preparation of efficient Cu₂S counter electrodes.

Tailorable boron-doped carbon nanotubes as high-efficiency counter electrodes for quantum dot sensitized solar cells

1. Tunable BCNTs are prepared by the pre-oxidation strategy. 2. B-Doped CNTs exhibit excellent activity for S_n²⁻ reduction. 3. The QDSSC based on CdS/CdSe QDs and BCNT1 shows a PCE of 4.55% under one sunlight illumination.

A novel strategy to design a multilayer functionalized Cu2S thin film counter electrode with enhanced catalytic activity and stability for quantum dot sensitized solar cells

As the essential component of a quantum dot-sensitized solar cell (QDSC), the counter electrode (CE) plays an important role in electron transfer and catalytic reduction acquisition throughout the device. A novel route to design multilayer functionalized Cu₂S thin films as CEs with high catalytic activity and enhanced stability, as well as large specific surface area and high conductivity, is presented. Firstly, Mo-based films were prepared by magnetron sputtering on a glass substrate, and then porous CuZnMo conductive films were formed by etching with hydrochloric acid. Secondly, indium tin oxide (ITO) film was sputtered onto the porous structure to act as a protective layer, and a porous ITO/CuZnMo structured film was obtained after optimization. In the third step, multilayer Cu(x)/ITO/CuZnMo structured films were acquired by sputtering Cu films. Finally, multilayer Cu₂S(t)/ITO/CuZnMo functionalized film CEs were obtained via in situ sulfidation of sputtered Cu films. The functions of conduction and resistance to electrolyte corrosion were produced and enhanced by annealing an ITO layer at high temperature prior to Cu deposition, while catalytic activity enabled by Cu₂S was realized from Cu film sulfidation. The multilayer Cu₂S/ITO(500 °C)/CuZnMo functionalized films exhibit high catalytic activity and enhanced stability for resistance to electrolyte corrosion. Taking multilayer Cu₂S/ITO(500 °C)/CuZnMo films as CEs, the QDSCs demonstrated good stability of power conversion efficiency (PCE) after 500 h of irradiation, from an initial 4.21% to a final 4.00%. Furthermore, the thickness of Cu₂S film modulated by the duration of Cu sputtering was investigated. It was found that the QDSCs using multilayer Cu₂S(40 min)/ITO/CuZnMo functionalized film with a Cu₂S thickness of 1.2 μm as CE exhibit the best performance, and the R _ct value was 0.57 Ω. The best photovoltaic performance with a PCE of 5.21% (V _oc = 533.1 mV, J _sc = 18.80 mA cm^-2, FF = 52.84%) was achieved under AM 1.5 radiation with an incident power of 100 mW cm^-2. This design of a multilayer functionalized CE introduces potential alternatives to the common brass-based CE for long-term QDSCs with high performance.

Anchoring CuS nanoparticles on accordion-like Ti3C2 as high electrocatalytic activity counter electrodes for QDSSCs

A Ti₃C₂/CuS composite has been fabricated as a counter electrode for quantum dot-sensitized solar cells by anchoring CuS nanoparticles on Ti₃C₂via a facile ion-exchange method at room temperature.