A₂‐A₁‐D‐A₁‐A₂‐Type Nonfullerene Acceptors

Abstract

The A2‐A1‐D‐A1‐A2‐type molecules consist of one electron‐donating (D) core flanked by two electron‐accepting units (A1 and A2) and have emerged as an essential branch of nonfullerene acceptors (NFAs). These molecules generally possess higher molecular energy levels and wider optical bandgaps compared with those of the classic A‐D‐A‐ and A‐DA'D‐A‐type NFAs, owing to the attenuated intramolecular charge transfer effect. These characteristics make them compelling choices for the fabrication of high‐voltage organic photovoltaics (OPVs), ternary OPVs, and indoor OPVs. Herein, the recent progress in the A2‐A1‐D‐A1‐A2‐type NFAs are reviewed, including the molecular engineering, structure‐property relationships, voltage loss (Vloss), device stability, and photovoltaic performance of binary, ternary, and indoor OPVs. Finally, the challenges and provided prospects are discussed for the further development of this type of NFAs.

Quinoxaline-based nonfullerene acceptors with powerful core-functionalization ability enabling efficient solar energy utilization

“…1–10 The π-conjugated nonfullerene electron acceptors (NFAs) composed of alternating electron-deficient and -rich units have triggered wide interest in solar energy exploitation because of their facile synthesis, structural diversity, controllable optoelectronic properties, and high mechanical flexibility. 11–17 The emergence of a star acceptor (ITIC) reported by Zhan's group has significantly promoted the development of NFAs, representing a milestone. 18 Nevertheless, the solar energy conversion efficiency will be affected by the intrinsic properties of organic light-harvesting materials, such as high exciton binding energies, small relative dielectric constants, defective intermolecular packing networks, or more crystal defects caused by the flexibility of large organic molecular skeletons, and so on.…”