Synthesis and Photovoltaic Properties of Quinoxaline-Based Semiconducting Polymers with Fluoro Atoms

Abstract

A new accepter unit, 6,7-difluoro-2,3-dihexylquinoxaline, was prepared and utilized for the synthesis of the conjugated polymers containing electron donor-acceptor pair for OPVs. New series of copolymers with dioctyloxybenzodithiophene as the electron rich unit and 6,7-difluoro-2,3-dihexylquinoxaline as the electron deficient unit are synthesized. The solid films of poly [2,6-(4,8-bis(2-ethylhexyloxy) , and fill factor (FF) of 0.39, giving power conversion efficiency (PCE) of 0.39%. To obtain absorption in the longer wavelength region, thiophene units without any alkyl group are incorporated as one of the monomers in PBDTQxF, which may result in low solubility of the polymers to lead lower efficiency.

Synthesis and Photovoltaic Properties of Copolymers with Fluorinated Quinoxaline and Fluorene Moiety

“…The UV-vis absorption spectra were recorded by a Varian 5E UV/VIS/NIR spectrophotometer. The cyclic voltammetry was performed with a sol- Carefully purified 9,9-bis(2-ethylhexyl)-2,7-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)fluorene ( 7) [17] (540 mg, 0.84 mmol), 5,8-bis (5-bromothiophen-2-yl)-6,7-difluoro-2,3-dihexylquinoxaline (6) [16] (550 mg, 0.84 mmol), P(o-tolyl)3 (40 mol%) and Pd2(dba)3 (3 mol%) were dissolved in 5 mL of chlorobenzene. The mixture was refluxed with vigorous stirring for 2 days under argon atmosphere.…”

“…The synthesis of the monomer and polymer are shown in Scheme 1. The monomers 6 and 7 were synthesized by reported method [16][17]. 5,8-Bis(5-bromothiophen-2-yl)-6,7-difluoro-2,3-dihexylquinoxaline (6) [16], as electron-deficient moiety and 9,9-bis(2-ethylhexyl)-2,7-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)fluorene ( 7) [17], as electron-rich moiety, were copolymerized according to Suzuki polymerization with Pd2(dba)3 as catalyst for 48 h to give target copolymer PFDTQxF.…”

Synthesis and photovoltaic properties of copolymers with a fluoro quinoxaline unit

“…Among the various donor units available, benzodithiophene has elicited much interest with respect to the design of novel‐conjugated polymers for use in PSCs, owing to its planarity and rigidity, which result from the fusion of its benzene ring with two thiophene units, as well as its good solubility, which is caused by its various side chains, and its high hole mobility . Quinoxaline‐based copolymers have been used for their ability to withdraw electrons from the nitrogen atoms in imine moieties and from their high solubility, which, as stated previously, results from their side chains . Recently, an electron‐withdrawing fluorine atom was introduced in quinoxaline to produce a low‐bandgap‐conjugated polymer with a relatively low HOMO energy level, to enhance the V OC of PSCs .…”

“…In this paper, we report the synthesis of D–A alternating copolymers with novel electron deficient units, namely, 6,7‐difluoro‐2,3‐dihexylquinoxaline and 6‐fluoro‐2,3‐dihexylquinoxaline, for use in high performance PSCs. It was assumed that the introduction of an F atoms into the quinoxaline moiety would lower the HOMO energy levels of the synthesized polymers and lead to an increase in V OC .…”

Photovoltaic polymers based on difluoroqinoxaline units with deep HOMO levels

“…Many of the low‐bandgap conjugated polymers have an electron‐withdrawing building block (e.g., benzothiadiazole (BT), 2 H ‐benzimidazole, diketopyrrolopyrrole and 6,7‐difluoroquinoxaline) and an electron‐donating moiety (e.g., such as carbazole, indenoindene, cyclopentaphenanthrene, and benzodithiophene . Benzodithiophene is a widely used electron donating materials because it readily undergoes polymerization and polymers of dialkoxy benzodithiophene provide high PCEs .…”