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A–D–A‐Type Oligothiophenes for Small Molecule Organic Solar Cells: Extending the π‐System by Introduction of Ring‐Locked Double Bonds
Author(s) -
Fitzner Roland,
MenaOsteritz Elena,
Walzer Karsten,
Pfeiffer Martin,
Bäuerle Peter
Publication year - 2015
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.201404210
Subject(s) - double bond , materials science , acceptor , organic solar cell , homo/lumo , ring (chemistry) , thiophene , molecule , energy conversion efficiency , crystallography , aromatization , steric effects , stereochemistry , polymer chemistry , optoelectronics , chemistry , polymer , catalysis , organic chemistry , physics , composite material , condensed matter physics
A series of novel acceptor–donor–acceptor oligothiophenes terminally substituted with the 1‐(1,1‐dicyanomethylene)‐cyclohex‐2‐ene (DCC) acceptor has been synthesized. Structural, thermal, optoelectronic, and photovoltaic properties of the π‐extended DCC n Ts ( n = 1–4) are characterized and contrasted to the trends found for the series of parent dicyanovinyl (DCV)‐substituted oligothiophenes DCV n T. The optoelectronic properties reveal the influence of the additional exocyclic, sterically fixed double bonds in trans ‐configuration in the novel DCC n T derivatives. A close correspondence for derivatives with equal number of double bonds, that is, DCC n Ts and DCV( n + 1)Ts, is identified. Despite having the same energy gap, the energy levels of the frontier orbitals, HOMO and LUMO, for the DCC ‐ derivatives are raised and more destabilized due to the aromatization energy of a thiophene ring versus two exocyclic double bonds indicating improved donor and reduced acceptor strength. DCC‐terthiophenes give good photovoltaic performance as donor materials in vacuum‐processed solar cells (power conversion efficiencies ≤ 4.4%) clearly outperforming all comparable DCV4T derivatives.