AUTHOR=Ramoroka Morongwa E. , Mdluli Siyabonga B. , John-Denk Vivian S. , Januarie Kaylin C. , Modibane Kwena D. , Nwambaekwe Kelechi C. , Yussuf Sodiq T. , Mokwebo Kefilwe V. , Williams Avril R. , Iwuoha Emmanuel I. 

TITLE=Synthesis and Reactivities of Conducting Hexathienylbenzene-Co-Poly(3-Hexylthiophene) Star-Branched Copolymer as Donor Material for Organic Photovoltaic Cell

JOURNAL=Frontiers in Materials

VOLUME=9

YEAR=2022

URL=https://www.frontiersin.org/journals/materials/articles/10.3389/fmats.2022.856008

DOI=10.3389/fmats.2022.856008

ISSN=2296-8016

ABSTRACT=<p>The hexathienylbenzene-co-poly(3-hexylthiophene-2,5diyl) (HTB-co-P3HT) conducting polymer was synthesized by oxidative co-polymerization of hexathienylbenzene (HTB) and 3-hexylthiophene using iron chloride (FeCl<sub>3</sub>) as an oxidant. The effect of chlorobenzene, toluene and chloroform on the optoelectronic characteristics of the polymer was investigated. The study revealed that spectroscopic and electrochemical responses of HTB-co-P3HT are affected by the nature of the solvent. The lowest unoccupied molecular orbital (LUMO) and highest occupied molecular orbital (HOMO) energy levels of HTB-co-P3HT were determined from cyclic voltammetry (CV) and were compared to those of (6,6)-Phenyl C71 butyric acid methyl ester (PC<sub>71</sub>BM) and it was found that the LUMO energy levels of HTB-co-P3HT in toluene were lower than those for chlorobenzene and chloroform. The electrochemical impedance spectroscopy (EIS) analysis also revealed the thin film of HTB-co-P3HT prepared using toluene as the most conductive. However, the photovoltaic parameters of the HTB-co-P3HT organic photovoltaic cells (OPVs) departed from the favored toluene and noted chlorobenzene as being the advantageous solvent. We obtained a power conversion efficiency (PCE) of 0.48%, fill factor (FF) of 27.84%, current density (J<sub><italic>SC</italic></sub>) of 4.93 mA.cm<sup>−2</sup> and open circuit voltage (V<sub><italic>OC</italic></sub>) of 0.35 V in chlorobenzene, a PCE of 0.30%, FF of 26.08%, J<sub><italic>SC</italic></sub> of 5.00 mA.cm<sup>−2</sup> and V<sub><italic>OC</italic></sub> of 0.23 V in chloroform and finally, a PCE of 0.33%, FF of 25.45%, J<sub><italic>SC</italic></sub> of 5.70 mA.cm<sup>−2</sup> and V<sub><italic>OC</italic></sub> of 0.23 V in toluene.</p>