We have fabricated highly efficient CdS/CdSe quantum dot-sensitized solar cells (QDSSCs) featuring low-cost cobalt sulfide (CoS) counter electrodes. Under 100 mW cm(-2) irradiation, the CdS/CdSe QDSSC featuring a CoS electrode provided an energy conversion efficiency as high as 3.4%.

Quantum dot-sensitized solar cells (QDSSCs) are interesting energy devices because of their (i) impressive ability to harvest sunlight and generate multiple electron/hole pairs, (ii) ease of fabrication, and (iii) low cost. The power conversion efficiencies (η) of most QDSSCs (typically <4%) are, however, less than those (up to 12%) of dye-sensitized solar cells, mainly because of narrow absorption ranges and charge recombination occurring at the QD-electrolyte and TiO(2)-electrolyte interfaces. To further increase the values of η of QDSSCs, it will be necessary to develop new types of working electrodes, sensitizers, counter electrodes and electrolytes. This Feature Article describes the nanomaterials that have been used recently as electronic conductors, sensitizers and counter electrodes in QDSSCs. The nature, size, morphology and quantity of these nanomaterials all play important roles affecting the efficiencies of electron injection and light harvesting. We discuss the behavior of several important types of semiconductor nanomaterials (sensitizers, including CdS, Ag(2)S, CdSe, CdTe, CdHgTe, InAs and PbS) and nanomaterials (notably TiO(2), ZnO and carbon-based species) that have been developed to improve the electron transport efficiency of QDSSCs. We point out the preparation of new generations of nanomaterials for QDSSCs and the types of electrolytes, particularly iodide/triiodide electrolytes (I(-)/I(3)(-)), polysulfide electrolytes (S(2-)/S(x)(2-)), and cobalt redox couples ([Co(o-phen)(3)(2+)/(3+)]), that improve their lifetimes. With advances in nanotechnology, we foresee significant improvements in the efficiency (η > 6%) and durability (>3000 h) of QDSSCs.

CuS, CoS, and CuS/CoS onto fl uorine-doped tin oxide glass substrates were deposited to function as counter electrodes for polysulfi de redox reactions in CdS/CdSe quantum dot-sensitized solar cells (QDSSCs). Relative to a Pt electrode, the CuS, CoS, and CuS/CoS electrodes provide greater electrocatalytic activity, higher refl ectivity, and lower charge-transfer resistance. Measurements of fi ll factor and short-current density reveal that the electrocatalytic activities, refl ectivity, and internal resistance of counter electrodes play strong roles in determining the energy-conversion effi ciency ( η ) of the QDSSCs. Because the CuS/CoS electrode has a smaller internal resistance and higher refl ectivity relative to those of the CuS and CoS electrodes, it exhibits a higher fi ll factor and short-circuit current density. As a result, the QDSSC featuring a CuS/CoS electrode provides a higher value of η . Under illumination of one sun (100 mW cm − 2 ), the QDSSCs incorporating Pt, CuS, CoS, and CuS/CoS counter electrodes provide values of η of 3.0 ± 0.1, 3.3 ± 0.3, 3.8 ± 0.2, and 4.1 ± 0.2%, respectively.

Although resistin has been thought to be an important link between obesity and diabetes, recent results do not support this hypothesis. We speculated that resistin may be involved in in£ammatory processes and be induced by in£amma-tory stimuli. In this study, we tested whether lipopolysaccharide (LPS) induced resistin expression in rats. The results show that resistin mRNA levels in white adipose tissue and white blood cells were increased by LPS treatment. LPS also increased resistin mRNA levels in 3T3-L1 adipocytes and human peripheral blood monocytes. The results suggest that resistin is involved in insulin resistance and probably in other in£ammatory responses.

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