Influence of alkyl chain length in S,N-heteropentacenes on the performance of organic solar cells

Abstract

Acceptor-substituted S,N-heteropentacenes with systematically varied alkyl side chains were prepared and implemented as donors in vacuum-processed OSCs giving devices with efficiencies in the range of 4–6%. An odd–even effect with respect to the length of the alkyl side chains is noted.

Synthesis and characterization of S,N-heterotetracenes

“…The absorption maximum (378 nm) and the shape of the band are comparable to those of SN6 (379 nm) [ 17 ]. The pronounced vibronic fine splitting of the main absorption bands is typical for the planar and stiff-fused backbones of the heteroacenes [ 20 ]. The optical gap, which is determined from the absorption onset, gradually decreases with increasing number of pyrrole rings in the heteroacenes from 3.62 eV for TTA to 3.50 eV for 33 ( Fig.…”

“…In the 1 H NMR spectra, the S,N-heterotetracenes typically showed two doublets with 3 J-coupling constants of 5.2-5.3 Hz for the α-and β-protons of the terminal thiophene units in the fused skeleton. Thereby the α-protons typically occur slightly downfield-shifted relative to the ß-protons [20]. If one compares the shifts of these protons of the basic systems TTA (H α 7.52, H ß 7.41 ppm) with those of SN4 13 (H α 7.39, H ß 7.33 ppm) and SN4'' 33 (H α 7.06, H ß 7.02 ppm), both protons gradually shift up-field the more electron-rich pyrrole rings are present in the system.…”

“…The highly planar π-conjugated systems revealed interesting structural features such as nearly complete bond length equalization and S-S and S-π dipolar interactions in the solid state. Due to tunable optoelectronic properties, a variety of functionalized derivatives, mainly trimeric DTP (SN3) [18], pentameric SN5 [19][20][21][22][23], and hexameric SN6 [24][25][26][27][28], have been successfully implemented as active semiconducting components in organic solar cells [18][19][20][21][24][25][26], perovskite solar cells [22,27], organic field-effect transistors [28], or sensors [23]. The interesting structure-property relationships of the S,N-heteroacene series inspired as well theoretical work.…”

S,N-Heteropentacenes – Syntheses of Electron-Rich Anellated Pentacycles

“…Interestingly, the solar cell efficiencies were influenced by the chain lengths of the aliphatic N-alkyl substituents with even numbered chain lengths exhibiting the best performances. 20 By a desymmetrization approach, efficiencies of this structure can be further enhanced (Scheme 4). Starting from the base structures 6 the unsymmetrical aldehydes 7 can be obtained by singular Vilsmeier-Haack formylation.…”

Defining side chain successions in anthracene-based poly(arylene ethynylene)-alt-poly(phenylene vinylene)s: probing structure–property relationships

“…8,18 As a consequence side chain engineering can serve as a highly potent tool to modify materials for optimized device performance. [19][20][21][22][23] Poly(arylene vinylene)s (PAVs) were the first group of conjugated polymers for which electroluminescence was reported, and are intensively investigated. 24 Poly(arylene ethynylene)s (PAEs) are more rigid structures with commonly enhanced photostability and high emission quantum yield in solution.…”