7-Azaisoindigo as a new electron deficient component of small molecule chromophores for organic solar cells

Abstract

The use of 7-azaisoindigo as an electron accepting moiety in donor-acceptor chromophores is reported for the first time. Four chromophores were synthesized that contained either 2,2 0-bithiophene or 3,3 0bis(dodecyloxy)-2,2 0-bithiophene as an electron-donating sub-unit and either isoindigo or 7azaisoindigo as an electron acceptor. The inclusion of a heteroatom in the isoindigo framework was designed to probe its effect on the LUMO, while 3,3 0-bis(dodecyloxy)-2,2 0-bithiophene was used as an electron rich alternative to 2,2 0-bithiophene in order to similarly evaluate its effect on the HOMO level. The electronic properties of the resulting chromophores were fully characterized by UV/visible spectroscopy, cyclic voltammetry, and density functional theory. All four dyes were evaluated for their performance as electron donors in bulk heterojunction solar cells using PC 61 BM as the electron acceptor. Devices that used the isoindigo and 3,3 0-bis(dodecyloxy)-2,2 0-bithiophene-based dye displayed the best performance, reaching a maximum power conversion efficiency of 0.93%.

Recent Advances in Isoindigo‐Inspired Organic Semiconductors

“…In heterocycle‐substituted isoindigos, the two benzene rings fused to the lactam units are replaced with heterocycles; the two most common heterocycle‐substituted variations are azaisoindigo and thienoisoindigo. The synthesis and use of 7‐azaisoindigo‐based semiconductors, which substitute the benzene ring for a nitrogen‐containing pyridine group, is where the Kelly Group made its entry into the field of isoindigo research …”

Azomethine naphthalene diimides as component of active layers in bulk heterojunction solar cells

“…Currently, three types of organic PV cells exist, that are, dye sensitized solar cells (DSSCs), planar organic semiconductor cells and bulk heterojunction (BHJ) cells [4]. However, as it was reported, the best of OPV devices are cells with BHJ architecture [5][6][7]. Typical BHJ cells consist of semiconducting polymer as electron donor material and soluble fullerene derivative [8].…”

“…Typical BHJ cells consist of semiconducting polymer as electron donor material and soluble fullerene derivative [8]. On the other hand, interest in small molecule BHJ cells is growing up [6,7,[9][10][11].…”

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

“…The first isoindigo based conjugated oligomeric D-A chromophore was reported by Reynolds et al [35]. Since then, a variety of isoindigo based D-A conjugated materials has been successfully incorporated in OSCs, affording relatively high efficiencies [36][37][38]. This includes both D-A oligomer and copolymer donor materials as well as n-type copolymers and dyes for metal-free dye-sensitized solar cells.…”