Modification on the Quinoxaline Unit to Achieve High Open-Circuit Voltage and Morphology Optimization for Organic Solar Cells

Abstract

Core engineering plays a vital role in the construction of efficient non-fullerene acceptors. Here, we synthesized a molecule named QX, based on the core of quinoxaline, and by replacing the H atoms with 2-ethylhexyl, 2-(ethylhexyl)thiophene, and 2-(2-ethylhexyl)-3-fluorothiophene groups, we obtained other three non-fullerene acceptors, named QX-EH, QX-TH, and QX-THF, respectively. Compared with QX, the introduction of substitution groups ameliorated the molecular solubility, and their lowest unoccupied molecular orbital levels were elevated. Also, the introduction of a thiophene ring in QX-TH and QX-THF enhanced their miscibility with PM6 compared to QX-EH. Furthermore, the introduction of a fluorine atom in QX-THF greatly optimized the blend morphology, leading to efficient charge transport, less bimolecular recombination, and suitable nanophase aggregation in devices. Eventually, PM6:QX-THF-based devices exhibited an impressive power conversion efficiency of 17.45% with a fill factor of 78.99%. This work reveals that modification on the quinoxaline core is effective in tuning the morphology and open-circuit voltage for high-efficiency organic photovoltaics.

Efficient Polymer Solar Cells Enabled by A-DA′D-A Type Acceptors with Alkoxypheny-Substituted Quinoxaline as the Fused-Ring Core

“…al synthesized two SMEAs Qx-1 and Qx-2, achieving a high PCE of 18.2% along with an excellent V OC of 0.934 V in PM6:Qx-2 device. Recently, Ge et al also reported four Qx-modified BTP-eC9-based SMEAs, namely, QX, QX-EH, QX-TH, and QX-THF, realizing an utmost PCE of 17.45% on the PM6:QX-THF binary PSCs and a promising V OC of 0.902 V. These achievements demonstrate the critical impacts of the quinoxaline structure on the photovoltaic performances of the resultant A-DA′D-A SMEAs-based PSCs.…”

Isomerization strategy on a non-fullerene guest acceptor for stable organic solar cells with over 19% efficiency

“…According to our previous work, the thienyl-substituted quinoxaline unit was chosen as the central electron-deficient core, which could provide a higher V OC and better film morphology. 33 Moreover, the rotatable thiophene-groups were fused to enhance the rigidity of the molecules and extend the p-conjugation skeleton. 34 Herein, two Y6-derivatives with isomeric central electron-deficient cores, QX-a and QX-g, with different orientations of their fused thiophene-rings were designed and synthesized to investigate the influence of the isomers in non-fullerene guest acceptors on their photovoltaic properties.…”

High‐Efficiency Organic Solar Cells Enabled by Chalcogen Containing Branched Chain Engineering: Balancing Short‐Circuit Current and Open‐Circuit Voltage, Enhancing Fill Factor

“…Choosing PM6 as the electron donor material, the BTP‐2O ‐based devices showed a PCE of 16.1%, with an outstanding V OC of 0.965 V, a J SC of 22.0 mA cm −2 , and a FF of 0.756, meanwhile, the BTP‐2S ‐based devices delivered a slightly higher PCE of 16.4%, with an increased J SC of 25.9 mA cm −2 , a decent FF of 0.743 but a markedly decreased V OC of 0.851 V. Astonishingly, the BTP‐O‐S ‐based devices exhibited a well‐balance between V OC (0.912 V) and J SC (24.5 mA cm −2 ), while achieving the highest FF of 0.775 and thus the best PCE of 17.3% in three of them, due to efficient exciton dissociation, suppressed charge recombination, high charge transport, and alleviative V loss . The PCE of 17.3% for the BTP‐O‐S ‐based devices is one of the highest efficiency reported for OSCs with high V OC surpassing 0.9 V. [ 44–46 ] Furthermore, the o ‐xylene ( o ‐XY) processed BTP‐O‐S ‐based devices yielded an excellent performance of 17.1%, which represents one of the highest efficiencies of binary OSCs via nonhalogenated solvent processing. Our work provides a feasible chalcogen containing branched chain engineering strategy to synergistically enhance absorption, matching energy levels, and optimize molecular arrangement leading to simultaneously achieving a better trade‐off between V OC and J SC .…”