Aryl-Substituted Boron Subphthalocyanines and their Application in Organic Photovoltaics

Abstract

A family of five axial aryl-substituted boron subphthalocyanine (BsubPc) derivatives bearing a hydrido, methyl, methoxy, phenyl, or fluoro substituent at the para position of the aryl were synthesised from Br-BsubPc and the corresponding aryl Grignard reagent in moderate yields. The physicochemical characterisation of these derivatives gave similar absorption, photoluminescence, and cyclic voltammetry profiles and photoluminescence quantum yields, indicating that the nature of the substituent at the para position does not influence the basic photophysical properties of this generic class of BsubPcs. Conversely, the solid-state structural arrangement obtained from single crystals is highly dependent on the para substituent; for the non-polar hydrido, methyl, and phenyl substituents, only concave isoindole π interactions are present. Substitution for the polar methoxy or fluoro ligand affords one-dimensional ribbons formed by convex π interactions, where these ribbons further interact through concave isoindole π interactions with the adjacent ribbon, creating an extended two-dimensional π network. On incorporation of the hydrido, methyl, and fluoro derivatives into organic photovoltaic (OPV) devices, similar results and device metrics were obtained with the methyl and fluoro derivatives. Both, however, were significantly outperformed by the hydrido derivative. The uniqueness of the hydrido derivative is only realised once incorporated into OPVs as it shares the same basic physical properties as the other derivatives. Given these findings, we identify the hydrido derivative as the aryl-BsubPc with the most promise for future work in OPVs.

Ring Opening Reactions through C-O Bond Cleavage Uniquely Adding Chemical Functionality to Boron Subphthalocyanine

“…During our study we saw only a moderate yield in the reaction of Br-BsubPc with phenyl-MgBr (Scheme 1). The resulting phenyl-BsubPc was found to have application in photovoltaic cells [21]. However, during this study we also identified an interesting side product during the attempted reaction of fluorophenyl Grignard reagents with Br-BsubPc (Scheme 1).…”

“…In our attempts to prepare BsubPc derivatives for organic electronic applications, we have explored Br-BsubPc as a starting material to react with various aryl Grignard reagents in anhydrous THF under reflux conditions (Scheme 1) [21]. After 16 h, HPLC analysis of the crude reaction mixture showed that, in addition to the desired axially-substituted aryl-BsubPc product ( 1 ), an impurity ( 2 ) was present in a significant quantity (>30%).…”

Boron Subphthalocyanines and Silicon Phthalocyanines for Use as Active Materials in Organic Photovoltaics

“…Results demonstrated that α‐6T is suitable as a standard electron donor to pair with BsubPc derivatives in vacuum deposited PHJ devices, with even α‐6T/Cl‐Cl 6 BsubPc outperforming α‐6T/C 60 despite significant V OC losses. Several novel BsubPc derivatives were synthesized and paired with an α‐6T in subsequent studies . The ability to fine‐tune the V OC through peripheral chlorination was also demonstrated, although pairing α‐6T with BsubPcs with deep LUMO energy levels (Cl‐Cl 6 BsubPc, Cl‐Cl 12 BsubPc) substantially reduces the V OC and overall OPV performance.…”

“…Bonnier et al . proceeded to synthesize five aryl‐substituted BsubPc derivatives, three of which (phenyl‐, 4‐tolyl‐, and 4‐fluorophenyl‐BsubPc, (Figure b ) ) were paired with α‐6T to evaluate their potential as an electron accepting layer . Phenyl‐BsubPc was discovered to outperform the other two aryl‐substituted BsubPc OPVs, with a PCE of 2.89 %.…”

International Year of Light and Light-Based Technologies

“…[19] Tim Bender and co-workers describe novel light-absorbing arylsubstituted boron subphthalocyanines. [20] Seth Rasmussen and colleagues report the influence of side chains and spacer units in light-absorbing thieno [3,4-b]pyrazine-flourene copolymers, [21] and David Lewis et al describe the effect of fullerene content in polymers. [22] Kenneth Ghiggino and his team report a new lightabsorbing copolymer based on benzodithiophene and [3,4-c] pyrrole-4,6-dione.…”