Quantum Chemical Calculations of Side-Group Stacking and Electronic Properties in Thiophene–Quinoxaline Polymers
2012-12-27T00:00:00Z (GMT)
by
Organic bulk heterojunction (BHJ) solar cells offer a
viable source
of solar energy. Structural organization is crucial in BHJ cells but
hard to achieve and assess due to limitations in experimental methodology.
Quantum chemical methods have here been used to gain further insight
into the geometric and optical properties of a promising light-harvesting
polymer, poly[2,3-bis(3-octyloxyphenyl)quinoxaline-5,8-diyl-alt-thiophene-2,5-diyl] (TQ1). Calculations show that favorable
positions of the two alkoxyphenyl side groups on each TQ1 monomer
allow nonbonded side-group stacking interactions with the neighboring
units in both directions. This yields a unique, helical geometry with
enhanced intramolecular ordering that promotes extensive electronic
conjugation. Adequate description of this effect requires computational
methods that include dispersion corrections. A strategy based on such
side-group interactions is proposed for designing new polymers.
