SYNTHESIS OF THIOPHENE π-BRIDGE MODIFIED BENZODITHIOPHENE AND QUINOXALINE BASED CONJUGATED POLYMERS FOR ORGANIC BULK HETEROJUNCTION SOLAR CELL APPLICATIONS

Date

2025-6-13

Author

Türkatar, Meltem

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In this study, six different donor-acceptor type benzodithiophene–quinoxaline-based conjugated polymers were synthesized via Stille cross-coupling reaction, incorporating a thiophene π-bridge, to investigate the effect of monofluorinated, difluorinated and dichlorinated quinoxaline units on device performance. Structural diversity was achieved by employing two distinct BDT cores one bearing a thienothiophene unit synthesized during this study, and the other a commercially available BDT with chlorine-substituted side chains, alongside systematic variation of halogen substituents on the quinoxaline unit. The six polymers are systematically categorized based on their quinoxaline halogenation and BDT core structures: P1, P3, and P5 incorporate a thienothiophene-based BDT unit, while P2, P4, and P6 utilize a chlorine-substituted BDT. Regarding the acceptor moiety, P1 and P2 feature difluorinated quinoxaline, P3 and P4 contain dichlorinated quinoxaline, and P5 and P6 are based on monofluorinated quinoxaline. The synthesized polymers were characterized using Nuclear Magnetic Resonance (NMR), Gel Permeation Chromatography (GPC), Thermal Gravimetric Analysis (TGA), UV-Vis Spectrometry, and Differential Pulse Voltammetry (DPV). The polymers exhibited Egᵒᵖ values of 1.72–1.98 eV and HOMO/LUMO levels ranging from −5.62/−3.86 to −6.26/−3.81 eV. The synthesized polymers were employed in the fabrication of organic solar cell devices using an architecture consisting of ITO/PEDOT:PSS/Donor:Acceptor/PDINN or PDINO/Ag. Conjugated polymer:acceptor-based organic solar cells were fabricated in a nitrogen-filled glove box, and their current–voltage characteristics were analyzed under AM 1.5G light using a solar simulator.The performances of the best devices are 5.99% for P1, 8.16% for P2, 1.48% for P3, 4.84% for P5, and 7.02% for P6.

Subject Keywords

Benzodithiophene, Thiophene, Quinoxaline, Solar Cells, Polymers

URI

https://hdl.handle.net/11511/115111

Collections

Graduate School of Natural and Applied Sciences, Thesis