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Effects of Shortened Alkyl Chains on Solution‐Processable Small Molecules with Oxo‐Alkylated Nitrile End‐Capped Acceptors for High‐Performance Organic Solar Cells
Author(s) -
Deng Dan,
Zhang Yajie,
Yuan Liu,
He Chang,
Lu Kun,
Wei Zhixiang
Publication year - 2014
Publication title -
advanced energy materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.08
H-Index - 220
eISSN - 1614-6840
pISSN - 1614-6832
DOI - 10.1002/aenm.201400538
Subject(s) - materials science , stacking , alkyl , acceptor , organic solar cell , polymer solar cell , nitrile , molecule , side chain , small molecule , miscibility , differential scanning calorimetry , chemical engineering , energy conversion efficiency , polymer chemistry , polymer , organic chemistry , optoelectronics , chemistry , biochemistry , physics , engineering , composite material , thermodynamics , condensed matter physics
Solution‐processable small molecules are significant for producing high‐performance bulk heterojunction organic solar cells (OSCs). Shortening alkyl chains, while ensuring proper miscibility with fullerene, enables modulation of molecular stacking, which is an effective method for improving device performance. Here, the design and synthesis of two solution‐processable small molecules based on a conjugated backbone with a novel end‐capped acceptor (oxo–alkylated nitrile) using octyl and hexyl chains attached to π–bridge, and octyl and pentyl chains attached to the acceptor is reported. Shortening the length of the widely used octyl chains improves self‐assembly and device performance. Differential scanning calorimetry and grazing incidence X‐ray diffraction results demonstrated that the molecule substituted by shorter chains shows tighter molecular stacking and higher crystallinity in the mixture with 6,6‐phenyl‐C 71 ‐butyric acid methyl ester (PC 71 BM) and that the power conversion efficiency (PCE) of the OSC is as high as 5.6% with an open circuit voltage ( V oc ) of 0.87 V, a current density ( J sc ) of 9.94 mA cm ‐2 , and an impressive filled factor (FF) of 65% in optimized devices. These findings provide valuable insights into the production of highly efficient solution‐processable small molecules for OSCs.