Nanostructured liquid-crystalline (LC) electrolytes have been developed for efficient and stable quasi-solid-state dye-sensitized solar cells (DSSCs). Two types of ionic LC assemblies for electrolytes have been designed: (i) noncovalent assemblies of two-component mixtures consisting of I2-doped imidazolium ionic liquids and carbonate-terminated mesogenic compounds (noncovalent type) and (ii) single-component mesogenic compounds covalently bonding an imidazolium moiety doped with I2 (covalent type). These mesogenic compounds are designed with flexible oligooxyethylene spacers connecting the mesogenic and the polar moieties. The oligooxyethylene-based material design inhibits crystallization and leads to enhanced ion transport as compared to alkyl-linked analogues due to the higher flexibility of the oligooxyethylene spacer. The noncovalent type mixtures exhibit a more than 10 times higher I3 – diffusion coefficient compared to the covalent type assemblies. DSSCs containing the noncovalent type liquid crystals show power conversion efficiencies (PCEs) of up to 5.8 ± 0.2% at 30 °C and 0.9 ± 0.1% at 120 °C. In contrast, solar cells containing the covalent type electrolytes show significant increase in PCE up to 2.4 ± 0.1% at 120 °C and show superior performance to the noncovalent type-based devices at temperature above 90 °C. Furthermore, the LC-DSSCs exhibit excellent long-term stability over 1000 h. These novel electrolyte designs open unexplored paths for the development of DSSCs capable of efficient conversion of light to electricity in a wide range of temperatures.

Non-centrosymmetric superconductor Re 6 Zr has attracted much interest, for its possible unconventional superconducting state with time reversal symmetry broken. Here we report the 185/187 Re nuclear quadrupole resonance (NQR) measurements on Re 6 Zr (T c = 6.72 K) and the isostructural compounds Re 27 Zr 5 (T c = 6.53 K) and Re 24 Zr 5 (T c = 5.00 K). The nuclear spin-lattice relaxation rate 1/T 1 shows a coherence peak below T c and decreases exponentially at low temperatures in all three samples. The superconducting gap ∆ derived from the 1/T 1 data is 2∆ = 3.58 k B T c , 3.55 k B T c , and 3.51 k B T c for Re 6 Zr ,Re 27 Zr 5 , and Re 24 Zr 5 , respectively, which is close to the value of 3.53 k B T c expected for weak-coupling superconductivity. These data suggest conventional s-wave superconductivity with a fully-opened gap in this series of compounds.

In many cases, unconventional superconductivity are realized by suppressing another order parameter, such as charge density wave (CDW) or spin density wave (SDW). This suggests that the fluctuations of these order parameters play an important role in producing superconductivity. LaPt2Ge2 undergoes a tetragonal-to-monoclinic structural phase transition (SPT) at Ts = 394 K, accompanying a double period modulation in the a-axis direction, and superconducts at Tc = 0.41 K. We performed band calculations and found 2D (two dimensional)-like Fermi surfaces with partial nesting. A reduction in the density of states in the monoclinic phase was found in the calculation and confirmed by 195 Pt-NMR. We suggest a CDW as a possible cause for the SPT. By changing the stoichiometry between Pt and Ge, we succeeded in suppressing Ts and increasing Tc in LaPt2−xGe2+x. Comparison of 139 La-and 195 Pt-NMR data reveals moderate fluctuations associated with SPT. From 139 La-NQR measurements at zero field, we found that an isotropic superconducting gap is realized in LaPt2−xGe2+x (x = 0.20). We discuss the relationship between superconductivity and the SPT order/fluctuations.