Journal of the American Chemical Society · 2011 · 1.5K citations · 29 references
Natural SciencesChemistryMaterials ScienceMaterials ChemistryOrganic ChemistryPolymer ChemistryConducting PolymersOrganic Electronic MaterialsOrganic SemiconductorsPhotovoltaic MaterialsSolar Cell MaterialsSolar CellsBand GapBulk Heterojunction Solar CellsConjugated PolymersOrganic Photovoltaic CellsOrganic PhotovoltaicsOrganic Solar CellsPhotovoltaic EfficiencyTandem Solar Cells
Recent advances in conjugated polymers for photovoltaics have focused on low band‑gap materials, yet an optimal band‑gap is only one of many criteria for high performance. This study aims to design two medium band‑gap (~2.0 eV) copolymers for photovoltaic cells. The copolymers are engineered to possess high hole mobility and low HOMO/LUMO energy levels. The fluorinated polymer PBnDT‑FTAZ delivers over 7 % power‑conversion efficiency with PC61BM, maintains >6 % at 1 µm thickness, surpasses P3HT, and shows that factors beyond low band‑gap contribute to high efficiency.
Recent research advances on conjugated polymers for photovoltaic devices have focused on creating low band gap materials, but a suitable band gap is only one of many performance criteria required for a successful conjugated polymer. This work focuses on the design of two medium band gap (∼2.0 eV) copolymers for use in photovoltaic cells which are designed to possess a high hole mobility and low highest occupied molecular orbital and lowest unoccupied molecular orbital energy levels. The resulting fluorinated polymer PBnDT−FTAZ exhibits efficiencies above 7% when blended with [6,6]-phenyl C61-butyric acid methyl ester in a typical bulk heterojunction, and efficiencies above 6% are still maintained at an active layer thicknesses of 1 μm. PBnDT−FTAZ outperforms poly(3-hexylthiophene), the current medium band gap polymer of choice, and thus is a viable candidate for use in highly efficient tandem cells. PBnDT−FTAZ also highlights other performance criteria which contribute to high photovoltaic efficiency, besides a low band gap.
29