Synthesis and Characterization of Conjugated Polymers Incorporating Fluorinated Phenazine for Application in Polymer Solar Cells

Abstract

Photovoltaic cells are crucial for harnessing solar energy and converting it into usable electrical power. This research focuses on the development of D-A type polymer solar cell acceptors based on fluorinated phenazine. We synthesized four distinct polymers: PBDT-DT-DoDFPz and PBDTT-DT-DoDFPz with linear alkyl side chains, and PBDT-DT-DHDFPz and PBDTT-DT-DHDFPz with branched alkyl side chains. The polymers PBDTT-DT-DoDFPz and PBDTT-DT-DHDFPz, incorporating BDTT, showed deeper HOMO energy levels than PBDT-DT-DoDFPz and PBDT-DT-DHDFPz, which feature BDT. Additionally, the branched phenazine units in PBDT-DT-DHDFPz and PBDTT-DT-DHDFPz resulted in lower HOMO levels compared to the linear phenazine in PBDT-DT-DoDFPz and PBDTT-DT-DoDFPz, enhancing the open-circuit voltage (Voc). AFM imaging revealed that PBDT-DT-DoDFPz and PBDTT-DT-DoDFPz with linear side chains formed more uniform and smaller domains when DCB was used, while PBDT-DT-DHDFPz and PBDTT-DT-DHDFPz with branched side chains demonstrated better domain uniformity with a 3% DIO additive. The final device optimization yielded a short-circuit current density (J_sc) of 9.36 mA/cm², a V_oc of 0.66 V, and an FF of 0.55%, resulting in a maximum PCE of 3.41%.