Abstract
Direct C-H arylation coupling is potentially a more economical and sustainable process than conventional cross-coupling. However, this method has found limited application in the synthesis of organic dyes for dye-sensitized solar cells. Although direct C-H arylation is not an universal solution to any cross-coupling reactions, it efficiently complements conventional sp2−sp2 bond formation and can provide shorter and more efficient routes to diketopyrrolopyrrole dyes. Here, we have applied palladium catalyzed direct C-H arylation in the synthesis of five new 3,6-dithienyl diketopyrrolopyrrole dyes. All prepared sensitizers display broad absorption from 350 nm up to 800 nm with high molar extinction coefficients. The dye-sensitized solar cells based on these dyes exhibit a power conversion efficiency in the range of 2.9 to 3.4%.
Highlights
The development of metal-free organic dyes with tunable optoelectronic properties is of importance among others, in the field of dye-sensitized solar cells (DSSCs)
Direct C-H arylation has been extensively employed in the synthesis of conjugated polymers for organic photovoltaics (OPVs) and organic field effect transistor applications (OFETs) [9,10,11], and has been used for preparation of metal-free organic dyes [12,13,14,15,16,17]
Diketopyrrolopyrroles are an interesting dye class as they have a broad and intense spectral absorption in the visible and NIR region. Such dyes have until now been synthesized by conventional cross-coupling methodologies
Summary
The development of metal-free organic dyes with tunable optoelectronic properties is of importance among others, in the field of dye-sensitized solar cells (DSSCs). Metal-free organic dyes are conventionally synthesized via sequential transformation of building blocks using transition metal-catalyzed cross-coupling reactions, such as Suzuki-Miyaura [4,5] and Migita–Kosugi–Stille couplings [6,7,8]. Despite their great versatility, these protocols often require the preparation of more advanced and expensive or toxic organometallic functionalized units such as arylene boronic acid/boronic esters for Suzuki and aryl stannanes for Stille-type reactions.
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