With a new metal-free donorÀacceptor photosensitizer featuring the 2,6-bis(thiophen-2-yl)-4,4-dihexyl-4H-cyclopenta [2,1-b:3,4-b 0 ]dithiophene-conjugated spacer and the tris(1,10-phenanthroline)cobalt(II/III) redox shuttle, we present a highly efficient iodine-free dyesensitized solar cell displaying a power conversion efficiency of 9.4% measured at 100 mW cm À2 simulated AM1.5 conditions. D ye-sensitized solar cells (DSCs) are presently under intense academic and industrial investigations because of their grand potential to serve as a low-cost alternative to existing photovoltaic technologies.1 A state-of-the art DSC fabricated by sensibly combining a panchromatic ruthenium dye, 2 an iodine electrolyte, and a thick mesoporous titania film has been notarized with a record solar-to-electricity conversion efficiency of 11.1% thus far.3 Owing to a resource restriction of the noble metal ruthenium, metal-free organic pushÀpull dyes have been actively pursued for the wide availability of their raw materials. 4 In this context, impressive progress on iodine-free DSCs displaying an excellent photovoltage has been attained very recently, based upon the combination of high-absorptivity organic dyes with either a solid organic hole-transporter 5 or some iron-, 6 cobalt-, 7 and copper-containing 8 redox shuttles, all of which feature considerably downward-shifted Fermi levels with respect to the common iodine electrolytes. However, these explorations have not yet afforded power conversion efficiencies comparable to those of champion DSCs based on organic dyes and iodine electrolytes.4dÀf In this work, we employ 2,6-bis(thiophen-2-yl)-4,4-dihexyl-4H-cyclopenta[2,1-b:3,4-b 0 ]dithiophene as the π-conjugated linker to synthesize a new dye, coded C229 ( Figure 1A), which exhibits outstanding efficiencies of 9.4À 10.3% in DSCs based on the tris(1,10-phenanthroline)cobalt electrolyte.In comparison with the C228 dye ( Figure 1A) possessing the 2,7-bis(thiophen-2-yl)-9,9-dihexylfluorene segment, C229 takes on an augmented maximum molar absorption coefficient at a desirable longer wavelength (as shown in Supporting Information (SI), Figure S1), owing to a better electron delocalizability of its π-conjugated spacer. 9 We further examined the photocurrent action spectra ( Figure 1B À2 simulated AM1.5 conditions. A (2.7+4.1)-μm-thick bilayer titania film was employed for cell fabrication. An antireflection film was adhered to a testing cell during measurement. All cells were measured with a metal mask having an aperture area of 0.158 cm 2 . The spectral distribution of our light resource simulates the AM1.5 solar emission (ASTM G173-03). The validity of our data is further confirmed by comparing the overlap integral of the measured IPCE spectrum with the standard AM1.5 solar emission spectrum and the experimental J sc , showing <5% error.

Six organic dyes with different conjugated linkers such as furan, bifuran, thiophene, bithiophene, selenophene, and biselenophene have been prepared in combination with the dihexyloxy-substituted triphenylamine donor and the cyanoacrylic acid acceptor. In conjunction with an acetonitrile-based electrolyte and a solvent-free ionic liquid electrolyte, these dyes exhibit 6.88−7.77% and 6.39−7.00% efficiencies, respectively. We have demonstrated that furan and selenophene can be employed as building blocks of sensitizers in stable solar cells for the first time. We have also studied the influence of heteroatoms on photocurrents and photovoltages with the aid of quantum calculations and transient photoelectrical decay measurements. Temperature-dependent electrical impedance experiments have shown that a relatively low external quantum efficiency of the dye with biselenophene linker is not related to the charge collection yield in the case of an acetonitrile electrolyte.

No abstract

No abstract

We scrutinize the energetic and kinetic interplays in oligothiophene dye-sensitized solar cells via analyzing electrical impedance as well as transient emission and absorption spectroscopies.

No abstract

A ruthenium sensitizer (coded C101, NaRu (4,4′‐bis(5‐hexylthiophen‐2‐yl)‐2,2′‐bipyridine) (4‐carboxylic acid‐4′‐caboxylate‐2,2′‐bipyridine) (NCS)2) containing a hexylthiophene‐conjugated bipyridyl group as an ancillary ligand is presented for use in solid‐state dye‐sensitized solar cells (SSDSCs). The high molar‐extinction coefficient of this dye is advantageous compared to the widely used Z907 dye, (NaRu (4‐carboxylic acid‐4′‐carboxylate) (4,4′‐dinonyl‐2,2′‐bipyridine) (NCS)2). In combination with an organic hole‐transporting material (spiro‐MeOTAD, 2,2′,7,7′‐tetrakis‐(N,N‐di‐p‐methoxyphenylamine) 9, 9′‐spirobifluorene), the C101 sensitizer exhibits an excellent power‐conversion efficiency of 4.5% under AM 1.5 solar (100 mW cm−2) irradiation in a SSDSC. From electronic‐absorption, transient‐photovoltage‐decay, and impedance measurements it is inferred that extending the π‐conjugation of spectator ligands induces an enhanced light harvesting and retards the charge recombination, thus favoring the photovoltaic performance of a SSDSC.

No abstract