Methyl-Branched Side Chains on Polythiophene Suppress Chain Mobility and Crystallization to Enhance Photovoltaic Performance
Journal
Macromolecules
Journal Volume
54
Journal Issue
8
Pages
3689-3699
Date Issued
2021
Author(s)
Chu J.-Y
Lin C.-Y
Tu T.-H
Hong S.-H
Chang Y.-Y
Yang C.-W
Chan Y.-T
Liu C.-L
Komarov P.V
Abstract
We synthesized a polythiophene with methyl-branched side chains, poly(3-2-methylpentylthiophene) (P3MPT), and studied the thermal properties, morphology, optoelectrical properties, and photovoltaic performance of P3MPT blended with the fullerene derivative, [6,6]-phenyl C60-butyric acid methyl ester (PCBM). The results are compared to those of the commonly used poly(3-hexylthiopene) (P3HT) with linear side chains to investigate the effects of the methyl-branched side chain. Differential scanning calorimetry (DSC) shows a higher glass transition temperature, and both X-ray diffraction and UV-vis absorption reveal a lower crystallization rate for P3MPT as compared to P3HT, due to the methyl-branched side chains that more efficiently suppress the chain mobility. Such behaviors can create an optimal as well as a stable structure for bulk-heterojunction solar cells so that the P3MPT/PCBM-based device not only shows a higher power conversion efficiency (PCE) but can much more effectively maintain the efficiency with time than the P3HT/PCBM-based device does. The stable phase-separated structure in the P3MPT/PCBM blend is confirmed by the grazing-incidence small-angle X-ray scattering (GISAXS) technique, which explains the superior long-term stability of the P3MPT/PCBM solar cell. ? 2021 American Chemical Society.
Subjects
Butyric acid; Conversion efficiency; Differential scanning calorimetry; Dye-sensitized solar cells; Efficiency; Glass transition; Heterojunctions; X ray scattering; Bulk heterojunction solar cells; Crystallization rates; Fullerene derivative; Grazing incidence small-angle X-ray scattering; Optoelectrical properties; Photovoltaic performance; Poly(3-hexylthiopene); Power conversion efficiencies; Polymer blends
SDGs
Other Subjects
Butyric acid; Conversion efficiency; Differential scanning calorimetry; Dye-sensitized solar cells; Efficiency; Glass transition; Heterojunctions; X ray scattering; Bulk heterojunction solar cells; Crystallization rates; Fullerene derivative; Grazing incidence small-angle X-ray scattering; Optoelectrical properties; Photovoltaic performance; Poly(3-hexylthiopene); Power conversion efficiencies; Polymer blends
Type
journal article