Simultaneous Tuning of Alkyl Chains and End Groups in Non-fused Ring Electron Acceptors for Efficient and Stable Organic Solar Cells

Abstract

Fine-tuning the alkyl chains and end groups of non-fused ring electron acceptors (NFREAs) plays vital roles in the promotion of charge transfer (CT) and power conversion efficiency (PCE). In this work, we developed a series of A−D−A′−D−A-type NFREAs, which possess the same terminals (A), the cyclopentadithiophene unit (D), and the thieno[3,4-c]pyrrole-4,6-dione (A′). Despite the subtle difference in side chains and halogenated end groups, the six acceptors exhibit a considerable difference in the efficiency and device stability of the organic solar cells (OSCs). Among the molecules, chlorinated NFREAs show a broader light absorption than the fluorinated ones do. Compared with C8C8−4F (1-octylnonyl and fluorination) and C6C4−4Cl (2-butyloctyl and chlorination), C8C8−4Cl (1-octylnonyl and chlorination) exhibits a lower highest occupied molecular orbital level, higher electron mobility, and denser molecular packing. The OSCs based on PM6:C8C8−4Cl yield the best PCE of 14.11%, which is attributed to the faster charge transport, high miscibility, and preferable morphology. Moreover, the PM6:C8C8−4Cl devices retain 91.1% of the initial PCE after being placed in air with 67% relative humidity for 50 days. This work shows that the simultaneous optimization of side chains and end groups facilitates the CT and improves the stability in the OSCs, offering a novel view into the molecular design of A−D−A′−D−A-type NFREAs.

Optimization of Alkyl Side Chain Length in Polyimide for Gate Dielectrics to Achieve High Mobility and Outstanding Operational Stability in Organic Transistors

“…Different alkyl side chains modification strategies ,, are often applied to organic semiconductor systems to improve their solubility and flexibility as well as adjust the molecular microstructure and charge transport behavior. Meanwhile, some researchers also elaborated on the effect of gate dielectrics based on metal or metal oxide surfaces with different alkyl chains length self-assembled monolayers on the device performance and stability of OTFTs. , These results proved that the alkyl chains’ chemical modification strategies in both organic semiconductors and inorganic dielectric layers can significantly influence the device performance.…”

“…Although some strategies have been taken to optimize PI chemical structures and preparation ways for improving the performance of OTFTs, low-temperature solution processing PI-based gate dielectrics for flexible OTFTs with high mobility (>1 cm 2 /Vs), relatively low operating voltage (<30 V), hysteresis-free behavior, and high operational stability remain a priority in this field of research. 14,28−32 Different alkyl side chains modification strategies 20,33,34 are often applied to organic semiconductor systems to improve their solubility and flexibility as well as adjust the molecular microstructure and charge transport behavior. Meanwhile, some researchers also elaborated on the effect of gate dielectrics based on metal or metal oxide surfaces with different alkyl chains length self-assembled monolayers on the device performance and stability of OTFTs.…”

Asymmetric non-fullerene acceptors enable high photovoltaic performanceviathe synergistic effect of carbazole-terminated alkyl spacer and halogen substitution

“…Meanwhile, the chlorinated Y6-SCz3 exhibited 15 nm red-shifted spectra (742 nm) relative to the fluorinated acceptors, which is attributed to the enhanced intramolecular charge transfer (ICT) effect in Y6-SCz3 . 24 Additionally, obvious bathochromic shifts of 69, 59, and 65 nm were observed for Y6-SCz1 , Y6-SCz2 , and Y6-SCz3 , respectively, yielding maximum absorption peaks in the order of Y6-SCz2 (790 nm) < Y6-SCz1 (803 nm) < Y6-SCz3 (813 nm), which are complementary to the absorption spectra of the PM6 donor polymer (Fig. 1c).…”

Side chain isomerization enables high efficiency and thickness tolerant organic solar cells

“…[1][2][3][4][5] To date, the power conversion efficiency (PCE) of OSCs has reached remarkable values exceeding 19% owing to the invention of new active layer materials, especially non-fullerene acceptors (NFAs) with acceptor-donor-acceptor (A-D-A) architectures [6][7][8][9][10][11][12][13] and efficient morphology control [14][15][16][17][18] for device fabrication and optimization. In the past decade, side chain engineering has proven to be an efficient method for the delicate design of active layer materials and precise regulation of the corresponding morphology because solubility, 19,20 crystallization 21 and packing modes, 22,23 etc. are substantially affected by the side chains of the active layer materials.…”