High-Performance Nonfused Electron Acceptor with Precisely Controlled Side Chain Fluorination

Abstract

Modification of the molecular packing of nonfullerene acceptors through fluorination represents one of the most promising strategies to achieve highly efficient organic solar cells (OSCs). In this work, three nonfused electron acceptors, namely, DTCBT-Fx (x = 0, 5, 9) with precisely controlled amounts of fluorine atoms in the side chains are designed and synthesized, and the effect of side chain fluorination is systematically studied. The results demonstrate that the light absorption, energy levels, molecular ordering, and film morphology could be effectively tuned by precisely controlling the side chain fluorination. DTCBT-F5 with an appropriate fluorine functionalization exhibits suitable miscibility with the donor polymer (PM6), leading to diminished charge recombination and improved charge carrier mobility. Consequently, a promising power conversion efficiency of 12.7% was obtained for DTCBT-F5-based solar cells, which outperforms those OSCs based on DTCBT-F0 (11.4%) and DTCBT-F9 (11.6%), respectively. This work demonstrates that precise control of the fluorine functionalization in side chains of nonfused electron acceptors is an effective strategy for realizing highly efficient OSCs.

Fine-Tuning of Polymer Aggregation Properties via Regulating the Side Chain Arrangement for Efficient Organic Solar Cells

“…Side chain engineering of organic semiconductors has been proved to be an effective method to realize highly efficient OSCs because the side chains have great influence on the optoelectronic properties, intermolecular interactions, and bulk heterojunction morphology. − It is found in previous researches that finely tuning the size, , isomerization, , adjusting the branching positions, desymmetrization, , or introducing chalcogen-containing alkyl chains on organic semiconductors can significantly affect their exciton dissociation, charge transport, and charge recombination in the devices, resulting in substantial differences in device performance. However, it is noted that these researches have mainly focused on state-of-the-art high-performance ladder-type nonfullerene SMAs during the past few years, whereas less attention has been focused on the side chains on the polymers.…”

Oligothiophene Additive‐Assisted Morphology Control and Recombination Suppression Enable High‐Performance Organic Solar Cells

“…Among various strategies employed to manipulate the BHJ morphology, the addition of a small amount of solvent additive into the main processing solvent(s) is acknowledged as a particularly straightforward yet effective method for achieving the desired morphology, with 1-chloronaphthalene (CN) and 1,8-diiodooctane (DIO) as the representative additives. [28][29][30][31][32] Nonetheless, it is worth noting that the introduction of CN and DIO often results in a decrease in the open-circuit voltage (V OC ) of the device, which may be attributed to the unfavorable vertical phase separation. [33,34] Besides, these additives often yield devices with compromised stability and reproducibility, because the residual trace amount of these additives cannot be completely eliminated due to their high boiling points.…”

Over 19 % Efficiency Organic Solar Cells Enabled by Manipulating the Intermolecular Interactions through Side Chain Fluorine Functionalization

“…Recent studies have shown that asymmetrical side chains can enhance the electronic coupling and mitigate the potential negative effects of over-fluorination. [31,32] Therefore, we designed and synthesized two asymmetric Y-series NFAs, BTP-F0 and BTP-F5, containing varying amounts of fluorine atoms in side chains (Figure 1a). Our results demonstrate that side chain fluorination can improve the overall average electrostatic potential (ESP) and charge balance factor to enhance the ESP-induced intermolecular electrostatic interaction of A/A and D/A, and thus finely modifying molecular ordering and bulk-heterojunction morphology.…”