Designing High-Performance Nonfused Ring Electron Acceptors via Synergistically Adjusting Side Chains and Electron-Withdrawing End-Groups

Abstract

Three nonfused ring electron acceptors, Hexyl-0F, Isopropyl-0F, and Isopropyl-2F, are designed and synthesized. Unlike Hexyl-0F, Isopropyl-0F with two sterically hindered 2,4,6triisopropyl-phenyl groups is highly soluble, which provides a good opportunity for solution processability. Compared with Isopropyl-0F, Isopropyl-2F with fluorinated end-groups exhibits red-shifted absorption. Due to these synergistic adjustment, Isopropyl-2Fbased devices displayed a high power conversion efficiency of 12.55%, higher than that of Isopropyl-0F (9.49%). The result demonstrates that the introduction of large steric substituents in the π-bridge units and electron-withdrawing end-groups plays a positive role in the construction of high-efficiency nonfused ring electron acceptors.

Non-covalent interactions (NCIs) in π-conjugated functional materials: advances and perspectives

“…An improvement in performance was noted when donor PBDB-T was replaced by poly[(2,6-(4,8 bis(5-(2-ethylhexyl-3-fluoro)thiophen-2-yl)-benzo[1,2- b :4,5- b ′] dithiophene))- alt -5,5′-(5,8-bis(4-(2-butyloctyl)thiophen-2-yl) di thieno[3′,2′:3,4;2′′,3′′:5,6]benzo[1,2- c ][1,2,5]thiadiazole)] (D18) (PCE = 12.55%). 84 The Δ E nr value was 0.27 and 0.29 eV for 40a and 40b , respectively. The CT property can also be modulated via an isomerization strategy.…”

Effect of Fluorinated End-Groups on the Exciton Dynamics and Charge Transfer of Non-fused Ring Acceptors

“…We also tested the absorption spectra and morphologies of their blend films in which they combined with donor PBDB-T in the previous publication. 35 When they are blended with donor PBDB-T, the position of their absorption peak is close to that of neat films, which reflects PBDB-T/Isopropyl-2F has the strong tendency of molecular stacking. According to AFM and TEM images, the PBDB-T/Isopropyl-2F blends formed slightly larger phase separation due to the enhanced crystallinities of Isopropyl-2F.…”

“…Compared with Isopropyl-0F, the absorption spectrum of Isopropyl-2F can be significantly red-shifted by the introduction of fluorine atoms on the end group. The PCE of an Isopropyl-2F-based device with PBDB-T as the donor polymer was 11.16%, which was higher than that of an Isopropyl-0F-based device (9.49%) . The results show that the introduction of fluorine atoms into the electron-withdrawing terminal group is beneficial to the construction of efficient NFREAs.…”

“…The PCE of an Isopropyl-2F-based device with PBDB-T as the donor polymer was 11.16%, which was higher than that of an Isopropyl-0F-based device (9.49%). 35 The results show that the introduction of fluorine atoms into the electronwithdrawing terminal group is beneficial to the construction of efficient NFREAs. However, the detailed physical mechanism for the differences in their performance is not answered.…”

Effect of Steric Hindrance at the Anthracene Core on the Photovoltaic Performance of Simple Nonfused Ring Electron Acceptors

“…In respect of molecular structures, the high-performance nonfullerene acceptors are usually of A-D-A or A-DA′D-A-type chemical structures. − These specific molecular features can induce a strong dipole moment and push the absorption spectrum to the near-infrared region, which is favorable for improving molecular packing and photon utilization. − However, nonfullerene acceptors sometimes suffer from low solubility, oversized packing, and the existence of large aggregates in blend films due to the too strong intermolecular interactions. − Generally speaking, there are several molecular design strategies to solve this problem. First, the introduction of bulky side chains, for example, ITIC with sp 3 hybrid aromatic chains as well as PTIC with sp 2 hybrid alkoxy and alkyl chains.…”