Tuning the photovoltaic performances of the terpolymers based on thiophene‐benzene‐thiophene via the modification of alkyl side chains

Abstract

Three new random conjugated terpolymers based on thiophene‐2,5‐bis((2‐ ethylhexyl)oxy)benzene‐thiophene or thiophene‐2,5‐bis((2‐octyl)oxy)benzene‐ thiophene as electron‐donating units, diketopyrrolopyrrole (DPP) and 4,7‐dithien‐5‐yl‐2,1,3‐benzothiadiazole (DTBT) side group as electron‐withdrawing units have been designed and synthesized by Stille‐coupling reaction. All the terpolymers exhibit good thermal stability, broad absorption in the range of 300 to 800 nm. By tuning the alkyl side chains of the terpolymers, the absorption spectra, HOMO energy levels and photovoltaic properties of the terpolymers changed dramatically. A bulk heterojunction polymer solar cell fabricated from terpolymer GP2 and PC61BM exhibited a promising power conversion efficiency of 3.31% without any processing additives. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 42982.

Impact of Alkyl Side Chains on Optoelectronic and Photovoltaic Properties of Novel Benzodithiophenedione‐Based Conjugated Polymers

“…Interestingly, polymer P2 with more branched 2‐hexyldecyl side chains demonstrated deeper lying HOMO than P1 with 2‐ethylhexyl substituents. This phenomenon was described previously and attributed to steric hindrance effects arising from the bulkier side chains, which induce slight twisting of the polymer backbone and reduce degree of delocalization along the conjugated backbone. Since the ultimate open‐circuit voltage ( V OC ) of OSCs is defined by the energy offset between the LUMO(acceptor) and HOMO(donor), the lower HOMO energy of P2 is beneficial to reach higher V OC in photovoltaic devices (Figure and Table ).…”

Bulk Heterojunction Solar Cells: The Role of Alkyl Side Chain on Nanoscale Morphology of Sulfur Over-rich Regioregular Polythiophene/Fullerene Blends

“…Thus, its accurate selection in order to achieve the optimal balance for maximum photoconversion efficiency (PCE) is required. 8 As far as the regioregularity of polyalkylthiophene derivatives is concerned, while the obtainment of head-to-tail (HT) regioregular polymeric derivatives requires handling of delicate synthetic procedures, 9,10 the preparation of head-to-head tail-to-tail (HH-TT) derivatives can be conveniently carried out through the popular iron trichloride oxidation procedure, starting from symmetrically substituted bithiophene monomers. Despite this, polymers containing only HH-TT junctions have been less investigated, since this regiochemistry favors backbone distortion and reduced electron delocalization.…”

“…Indeed, the alkyl side chain usually linked to the electron-donor polymeric moiety, in addition to favor solubility, processability, and compatibility with the fullerene acceptor, also affects the electronic properties, the crystallinity degree, and the overall physical structure of the material in the aggregated state. Thus, its accurate selection to achieve the optimal balance for maximum photoconversion efficiency (PCE) is required . As far as the regioregularity of polyalkylthiophene derivatives is concerned, while the obtainment of head-to-tail (HT) regioregular polymeric derivatives requires handling of delicate synthetic procedures, , the preparation of head-to-head tail-to-tail (HH-TT) derivatives can be conveniently carried out through the popular iron trichloride oxidation procedure, starting from symmetrically substituted bithiophene monomers.…”