Performance of dye-sensitized solar cells (DSCs) was investigated depending on the compositions of the electrolyte, i.e., the electrolyte with a different cation such as Li(+), tetra-n-butylammonium (TBA(+)), or 1,2-dimethyl-3-propylimidazolium (DMPIm(+)) in various concentrations, with and without 4-tert-butylpyridine (tBP), and with various concentrations of the I(-)/I(3)(-) redox couple. Current-voltage characteristics, electron lifetime, and electron diffusion coefficient were measured to clarify the effects of the constituents in the electrolyte on the charge recombination kinetics in the DSCs. Shorter lifetimes were found for the DSCs employing adsorptive cations of Li(+) and DMPIm(+) than for a less-adsorptive cation of TBA(+). On the other hand, the lifetimes were not influenced by the concentrations of the cations in the solutions. Under light irradiation, open-circuit voltages of DSCs decreased in the order of TBA(+)> DMPIm(+) > Li(+), and also decreased with the increase of [Li(+)]. The decreases of open-circuit voltage (V(oc)) were attributed to the positive shift of the TiO(2) conduction band potential (CBP) by the surface adsorption of DMPIm(+) and Li(+). These results suggest that the difference of the free energies between that of the electrons in the TiO(2) and of I(3)(-) has little influence on the electron lifetimes in the DSCs. The shorter lifetime with the adsorptive cations was interpreted with the thickness of the electrical double layer formed by the cations, and the concentration of I(3)(-) in the layer, i.e., TBA(+) formed thicker double layer resulting in lower concentration of I(3)(-) on the surface of the TiO(2). The addition of 4-tert-butylpyridine (tBP) in the presence of Li(+) or TBA(+) showed no significant influence on the lifetime. The increase of V(oc) by the addition of tBP into the electrolyte containing Li(+) and the I(-)/I(3)(-) redox couple was mainly attributed to the shift of the CBP back to the negative potential by reducing the amount of adsorbed Li cations.

Idiopathic pulmonary alveolar proteinosis (I-PAP) is a rare disease of unknown etiology in which the alveoli fill with lipoproteinaceous material. We report here that I-PAP is an autoimmune disease with neutralizing antibody of immunoglobulin G isotype against granulocyte/macrophage colony-stimulating factor (GM-CSF). The antibody was found to be present in all specimens of bronchoalveolar lavage fluid obtained from 11 I-PAP patients but not in samples from 2 secondary PAP patients, 53 normal subjects, and 14 patients with other lung diseases. It specifically bound GM-CSF and neutralized bioactivity of the cytokine in vitro. The antibody was also found in sera from all I-PAP patients examined but not in sera from a secondary PAP patient or normal subjects, indicating that it exists systemically in I-PAP patients. As lack of GM-CSF signaling causes PAP in congenital cases and PAP-like disease in murine models, our findings strongly suggest that neutralization of GM-CSF bioactivity by the antibody causes dysfunction of alveolar macrophages, which results in reduced surfactant clearance.

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A dye-sensitized solar cell fabricated using the room temperature molten salt, 1-hexyl-3-methylimidazolium iodide, iodine and a low molecular weight gelator as a quasisolid-state electrolyte showed a 5.0% light-to-electricity conversion efficiency under AM 1.5 irradiation, and high-temperature stability.

Dye-sensitized solar cells (DSCs) using ionic liquids, 1-alkyl-3-methylimidazolium iodide (alkyl:  C3−C9), were fabricated with and without a low molecular weight gelator. The highest energy conversion efficiency of 5.0% was obtained from a quasi-solid-state DSC using 1-hexyl-3-methylimidazolium iodide (HMImI). Gelation of these ionic liquids demonstrated better high-temperature durability without decreasing the solar cell efficiency. However, the short-circuit currents (J SC) obtained from these DSCs were about 70% of that obtained from DSCs using organic liquid electrolyte (OLE). To explain the difference of the J SC values between the DSCs using ionic liquid electrolyte (ILE) and OLE, four primitive processes in DSCs, that is, charge transport in the electrolytes, light absorption by I3 -, electron diffusion in a TiO2 electrode, and charge recombination, were examined. Viscosities of the ILE decreased with increasing I3 - concentration and alkyl chain length. In ILE, measured J SC values increased with increasing I3 - concentration up to 0.7−1.4 M, depending on the alkyl chain length. Measured J SC values showed the same tendency as that estimated using a calculation with a model in which the redox couple is transported by diffusion in electrolytes. These results suggest that the slower diffusion of I3 - to the counter electrode (CE) limits the J SC values and requires a larger amount of I3 - in ILE. However, increasing [I3 -] to more than 0.7−1.4 M resulted in the decrease of J SC. At the optimized concentration of I3 - in ILE, the influence of the absorption was estimated to be 13% of the decrease on photocurrent. To the estimate electron diffusion length in the TiO2 electrode, the electron diffusion coefficient (D e) and electron recombination lifetime (τ) were measured, showing faster D e and shorter τ in ILE than in OLE. The faster D e was caused by the higher concentration of cation in ILE. However, the shorter τ was caused by the higher concentration of I3 - and depended on the concentration. Thus, the electron diffusion lengths (L) in the DSC using ILE were shorter than that using OLE. Their shorter L also reduced the J SC in the ILE and with the increase of I3 - concentration. Among the ILE, the increase of alkyl chain length increased τ. This result should explain the highest efficiency observed in HMImI. During the durability test of the DSC at high temperature, a decrease of the efficiency of the cell using ILE was observed in 1000 h. Time course change of I3 - concentration measurements revealed that the gelation of the electrolyte depresses a decrease of I3 - concentration caused by sublimation of I2. Depression of sublimation of I2 is important to improve the high-temperature durability in nonvolatile ionic liquid electrolyte.