Efficient Dye-Sensitized Solar Cells with an Organic Photosensitizer Featuring Orderly Conjugated Ethylenedioxythiophene and Dithienosilole Blocks

Abstract

In view of the limited ruthenium resource, metal-free organic dyes may play a prominent role in the coming large-scale application of cost-effective dye-sensitized solar cells, if their efficiency and stability can be considerably improved. In this paper we utilized a binary π-conjugated spacer of ethylenedioxythiophene and dithienosilole to construct a high molar absorption coefficient push-pull dye, characteristic of an intramolecular charge-transfer band peaking at 584 nm measured in chloroform. In comparison with the standard ruthenium sensitizer Z907, this metal-free chromophore C219 endowed a nanocrystalline titania film with an evident light-harvesting enhancement, leading to an unprecedented 10.0-10.3% efficiency at the AM1.5G conditions for dyesensitized solar cells with nonruthenium dyestuffs, although a highly volatile electrolyte was used. Transient absorption measurements have revealed that even if the kinetics of back-electron transfer and dye regeneration are considerably different for Z907 and C219, the branching ratios of these two charge-transfer channels are over 35 for both dyes, ensuring a high yield of net charge separation at the titania/dye/electrolyte interface. A solvent-free ionic liquid cell with C219 as the sensitizer exhibited an impressive efficiency of 8.9% under a low light intensity of 14.39 mW cm -2 , making it very favorable for the indoor application of flexible dye-sensitized solar cells.

D-π-A Dye System Containing Cyano-Benzoic Acid as Anchoring Group for Dye-Sensitized Solar Cells

“…The solvent was removed and the residue was purified on a silica gel column with EtOAc/hexane (1/100, v/v) to obtain 2 in 60% yield (0.358 g). 1 Synthesis of Methyl 2-Cyano-4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzoate (4). A 100 mL flask with a magnetic stirring bar, a septum inlet, and a condenser was charged with Pd(dba) 2 (0.17 g, 0.3 mmol) and tricyclohexylphosphine (0.20 g, 0.72 mmol) under nitrogen.…”

“…After being stirred at 80°C for 19 h, the reaction mixture was treated with water (30 mL). The product was extracted with toluene, washed with brine, and dried over MgSO 4 . Removal of the solvent followed by trituration with methanol gave 4 as white solid in 45% yield (1.29 g).…”

Dithieno[2,3-d;2′,3′-d′]benzo[1,2-b;4,5-b′]dithiophene based organic sensitizers for dye-sensitized solar cells

“…6 To date, a strong electron-poor unit such as cyanoacrylic acid bearing an anchoring group toward the TiO 2 surface is widely applied as the acceptor moiety, 7 while electron-rich units such as aromatic amines, 8,9 carbazoles, 10 and coumarins 11 are mostly adopted as donors. In addition to these, it is equally signicant to judiciously modify the p spacer for modulating properties of the organic dyes.…”

New generation solar cells: concepts, trends and perspectives

“…Many different organic dyes, such as indolenes, perylenes, squarines, donor-acceptor (D-A) dyes, have been reported over the years, but efficiencies consistently remain in the range of 6-8% 85 with a few exceptions. The best performing metal-free organic sensitizers to date are D-A dyes C219, with a 10.1% PCE 86 and RK1 with 10.2% (Fig. 11).…”