Regioisomerically Pure 1,7-Dicyanoperylene Diimide Dimer for Charge Extraction from Donors with High Electron Affinities

Abstract

Perylene diimide (PDI) has attracted widespread interest as an inexpensive electron acceptor for photovoltaic applications; however, overcrystallization in the bulk heterojunction typically leads to low device performance. Recent work has addressed this issue by forming bay-linked PDI dimers and oligomers, where the steric bulk of adjacent PDI units forces the molecule to adopt a nonplanar structure. This disrupts the molecular packing and limits domain sizes in the bulk heterojunction. Unfortunately, the introduction of electron-donating/-withdrawing groups in the bay region is also the best way to fine-tune the frontier molecular orbitals (FMOs) of PDI, which is highly desirable from a device optimization standpoint. This competition for the bay region has made it difficult for PDI to keep pace with other non-fullerene acceptors. Here, we report the synthesis of regioisomerically pure 1,7-dicyanoperylene diimide and its dimerization through an imide linkage. We show that this is an effective strategy to tune the energies of the FMOs while simultaneously suppressing overcrystallization in the bulk heterojunction. The resulting acceptor has a low LUMO energy of −4.2 eV and is capable of accepting photogenerated electrons from donor polymers with high electron affinities, even when conventional acceptors such as PDI, PC 71 BM, and ITIC cannot.

Silylethynyl Substitution for Preventing Aggregate Formation in Perylene Diimides

“…The first of the two most well-known examples of these regioisomer synthesis methods starts with the synthesis of perylenetetraester (PTE) and dibromoperylenetraester (DBrPTE) and then conversion of the 1,7-isomeric DBrPTEs obtained by crystallization of the mixed-isomer 1,6 and 1,7-DBrPTE derivatives to 1,7-dibromoperylenetetracarboxylicdianhydride (DBrPTCDA). , In the second method, 1,6 and 1,7-regio isomers of diBrPDIs are synthesized from specific alkyl-amine derivatives and purified by column chromatography. The purified 1,6 or 1,7-DBrPDI derivatives are then hydrolyzed in basic medium and converted back into the DBrPTCDA derivatives.…”

Green Solvent-Processible N–H-Functionalized Perylene Diimide Materials for Scalable Organic Photovoltaics

“…Cyano groups can then be introduced using the Rosenmund–von Braun reaction to afford structures X4 and regioisomerically pure X5 . Cyanation of the bay region typically leads to regioisomeric scrambling, − and thus, this finding suggests that the presence of cyclized amines in the bay region can direct PDI functionalization. Structures of compounds X2–5 were confirmed using nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry with purity determined using CHN elemental analysis.…”

Perylene-diimide for organic solar cells: current scenario and prospects in molecular geometric, functionalization, and optoelectronic properties

“…112–114 Huge-scale synthesis and purification of these compounds are also not prohibitively expensive when done on a large scale. 115–117 In fullerene-free OSC research, we recently made functionalized PDI electron acceptors that dissolve well in organic solvents and high-performance solar cells with V OC s. 118–122 Electron donors in blending films can be substituted with electron donors in PDI s, which were synthesised by Xu et al in 2017. The electronic properties of the donor units influenced the fluorescence quantum yield and emission duration.…”