Effect of Electron-Withdrawing Chlorine Substituent on Morphological and Photovoltaic Properties of All Chlorinated D–A-Type Quinoxaline-Based Polymers

Abstract

The choice of the chlorine (Cl) atom as an electron-withdrawing substituent in conjugated polymers leads to a higher potential in the commercialization of polymer solar cells than its fluorine counterpart because of the versatility and cost-effectiveness of the chlorination process. In addition, the population and location of Cl substituents can significantly influence the photovoltaic characteristics of polymers. In this study, three chlorinated quinoxaline-based polymers were invented to examine the numerical and positioning effects of the Cl atom on their photovoltaic characteristics. The number of Cl substituents in the reference polymer, PBCl-Qx, was adjusted to three: two Cl atoms in the benzodithiophene-type D unit and one Cl atom in the quinoxaline-type A unit. Subsequently, two more Cl atoms were selectively introduced at the 4- and 5-positions of the alkylated thiophene moieties at the 2,3-positions of the quinoxaline moiety in PBCl-Qx to obtain the additional polymers PBCl-Qx4Cl and PBCl-Qx5Cl, respectively. The conventional PBCl-Qx4Cl device exhibited a better power conversion efficiency (PCE) of 12.95% as compared to those of PBCl-Qx (12.44%) and PBCl-Qx5Cl (11.82%) devices. The highest PCE of the device with PBCl-Qx4Cl was ascribed to an enhancement in the open-circuit voltage and fill factor induced by the deeper energy level of the highest occupied molecular orbital and the favorable morphological features in its blended film with Y6.

Hexagonal 2D covalent organic frameworks from nonpolar and symmetric electron-accepting substituents for electron transport layers in near-infrared PeLEDs

“…In Tp-DAAQ, electrons are more localized in the center at HOMO, while electrons are dispersed along the chain at LUMO, and this large difference between the HOMO and LUMO wave functions can facilitate the generation of intramolecular charge transfer. 54 We further calculated the EDMs and obtained values of 0 and 2.32 Debye in Tp-DAAQ and Tp-DABDA, respectively, indicating that Tp-DAAQ is a nonpolar molecule while Tp-DABDA is a polar molecule (Fig. 3a).…”

Recent Advances of Benzodithiophene‐Based Donor Materials for Organic Solar Cells

“…Chlorination can lower the HOMO lever of the polymer owing to the vacant d-orbitals for 𝜋-electron delocalization and decrease the non-radiative E loss by balancing V OC and J SC . [61][62][63][64] Replace the fluorination with chlorination, PM7 exhibits a deeper HOMO and superior optical properties than PM6, thus, the PM7-based OSCs obtained better performance than PM6-based OSCs even applied the same NFAs. Thus, the device with ITO/NP-ZnO/PM7: IT-4F/MoO 3 /Al was fabricated.…”