Hierarchical nanostructured spherical carbon with hollow core/mesoporous shell (HCMS) was explored as a counter electrode in CdSe quantum-dot-sensitized solar cells. Compared with conventional Pt electrodes and commercially available activated carbon, the HCMS carbon counter electrode exhibits a much larger fill factor due to the considerably decreased charge transfer resistance at the interface of the counter electrode/polysulfide electrolyte. Furthermore, a solar cell with the HCMS carbon counter electrode presents a high power conversion efficiency of up to 3.90% as well as an incident photon-to-current conversion efficiency peak of 80%.

A ruthenium complex (JK-142) with an ancillary bipyridyl ligand substituted by a 3-carbazole-2-thiophenyl moiety was synthesized and explored as a sensitizer in cosensitized solar cells in combination with an organic dye (JK-62). The extended π-conjugation in the ancillary ligand enables the JK-142 dye to have a red-shift light absorption band; however, the ineffective penetration of JK-142 molecules into the inner surface of TiO 2 film results in low photovoltaic performance for the single dye sensitized solar cell due to its large molecular size of JK-142. Interestingly, when the deficient JK-142 electrode was employed to assemble a cosensitized solar cell by additionally adsorbing JK-62 dye, a considerably improved efficiency of up to 10.2% was achieved, which is favorably superior to that (ca. 8.68%) of N719 in the same device configurations. The results shown here not only provide new vision on how to produce highly efficient solar cells using dyes with extended molecular structure but also open up a new way to position different dyes on a single TiO 2 film for cosensitization through controlling the molecule size.

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A quasi-solid-state dye-sensitized solar cell with novel organic sensitizers incorporating a benzothiadiazole chromophore showed excellent long-term stability, which exhibited 10% decrease during the 1000 h light soaking; the optimized cell gave a short circuit photocurrent density of 12.03 mA cm À2 , an open circuit voltage of 0.720 V and a fill factor of 0.76, corresponding to an overall conversion efficiency of 6.61% under standard global AM 1.5 solar conditions.

A new class of cyclometalated ruthenium sensitizers incorporating a ĈNN ligand and conjugated 2,2'-bipyridine in the ancillary ligand have been designed and synthesized. The photovoltaic performance of JK-206 using an electrolyte containing 0.6 M 1,2-dimethyl-3-propylimidazolium iodide, 0.05 M I(2), 0.1 M LiI, and 0.5 M tert-butylpyridine in CH(3)CN gave a short-circuit photocurrent density of 19.63 mA cm(-2), an open-circuit voltage of 0.74 V, and a fill factor of 0.72, affording an overall conversion efficiency of 10.39%. The efficiency is the highest one reported for dye-sensitized solar cells based on the cyclometalated ruthenium sensitizer of the type ĈNN. Moreover, the same device using a polymer gel electrolyte exhibited a remarkable stability under 1000 h of light soaking at 60 °C, retaining 91% of the initial efficiency of 7.14%.