Oligomers Comprising 2-Phenyl-2H-benzotriazole Building Blocks for Solution-Processable Organic Photovoltaic Devices

Abstract

In the past, benzotriazole acceptor units have been incorporated successfully into donor−acceptor polymers for highly efficient photovoltaic devices. Here, we explore 2phenyl-2H-benzotriazole oligomers as model systems for donor−acceptor polymers. We designed and synthesized acceptor−donor−acceptor oligomers incorporating 2-phenyl-2Hbenzotriazole acceptor and naphthodithiophene donor units. Supported by quantum chemical calculations we investigated the optoelectronic properties, such as electronic levels and intramolecular charge transfer, by means of optical and fluorescence spectroscopy. We built bulk-heterojunction solar cells comprising these oligomers and [6,6]-phenyl C 61 -butyric acid methyl ester. In doing so, the film-forming conditions were optimized as the absorber layer morphology is strongly affected by the deposition conditions, in particular drying time and drying temperature.

Introducing a new triazoloquinoxaline‐based fluorene copolymer for organic photovoltaics: Synthesis, characterization, and photovoltaic properties

“…Recently, benzotriazole (BTz) containing oligomers and polymers have attracted considerable attention in organic photovoltaics due to their functionality 14–21. Unlike benzothiadiazole (BTd), the benzotriazole moiety provides an advantage of incorporating alkyl chains or aryl substituents onto the acceptor unit, superior for keeping the polymer soluble.…”

Linear and propeller-like fluoro-isoindigo based donor–acceptor small molecules for organic solar cells

“…Amongst all the strategies used to reach those desired properties, the combination of electron-rich (donor, D) and electron-deficient (acceptor, A) repeating units, forming intramolecular donor-acceptor (D-A) structures, has been very successful for developing low bandgap materials with tuned frontier orbital energy levels [21]. Various D-A type small molecules based on a variety of electron-deficient groups such as squaraine [22], benzotriazole [23], alkyl cyanoacetate [24], diketopyrrolopyrrole [25], benzothiadiazole [26], and isoindigo [27], most often combined with electron-donating oligothiophenes and arylamines, have been reported. To date, the highest PCEs for small molecule:fullerene BHJ OSCs are in the range of 7-10% [28][29][30][31][32][33].…”

Modeling approach to derive the anisotropic complex refractive index of polymer:fullerene blends for organic solar cells utilizing spectroscopic ellipsometry

“…[13][14][15][16][17][18][19][20][21][22][23][24] Therefore, an urgent need for flexible optical descriptions of bulk-heterojunctions emerged, which use parametric descriptions and allow for individual adjustments.…”