Laboratory-size dye solar cells (DSCs), based on industrially feasible materials and processes employing liquid electrolytes, have been developed. Cells based on two electrolyte solvents with different physical properties were subjected to thermal stress test at 80 °C for 2000 h in the dark to monitor their long-term thermal stability. The DSCs incorporating a methoxypropionitrile (MPN)-based electrolyte presented a severe efficiency loss at 1 sun AM 1.5G of more than 70% upon thermal aging, while the solar cells using tetraglyme (TG) as a high boiling point solvent attained a promising stability with only 20% loss of performance. To better understand the above behavior, systematic experiments, including optical microscopy, linear sweep voltammetry, UV−vis absorption, electrochemical impedance, and Raman spectroscopies were conducted. Virtually no dye degradation/desorption, electrolyte decomposition, semiconductor passivation, or loss of cathode activity could be identified. For the MPN-based cells, a sharp decrease in the short-circuit photocurrent was observed at high illumination intensities following thermal stress, attributed to charge-transfer limitations due to severe triiodide loss, verified by different experimental techniques. These degradation effects were efficiently mitigated by replacing MPN with the high-boiling-point solvent in the electrolyte.

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In this letter, we report the results of field (H) and temperature (T) dependent magnetization (M) measurements of a pellet of uniform, large-grain sintered MgB 2 . We show that at low temperatures the size of the pellet and its critical current density, J c (H) --i.e. its M(H) --ensure low field flux jumping, which of course ceases when M(H) drops below a critical value. With further increase of H and T the individual grains decouple and the M(H) loops drop to lower lying branches, unresolved in the usual full M(H) representation. After taking into account the sample size and grain size, respectively, the bulk sample and the grains were deduced to exhibit the same magnetically determined J c s (e.g. 10 5 A/cm 2 , 20 K, 0T) and hence that for each temperature of measurement J c (H) decreased monotonically with H over the entire field range, except for a gap within the grain-decoupling zone.

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