Tetracyano-Bridged Chromophores: Efficient Nonfullerene Acceptors for Solar Cells

Recent rapiddevelopmentsin the design of nonfullerene acceptors (NFAs) have significantly enhanced the power conversion efficiency of organic solar cells (OSCs). Tetracyano-bridged chromophores [(tetracyanobutadiene (TCBD) and dicyanoquinodimethane (DCNQ)] have emerged as a promising class of materials, gaining widespread attention for the development of NFAs. This review focuses on advances in TCBD- and DCNQ-based molecules reported in the last few years as NFAs by highlighting their strong electron-accepting abilities, tunable broad absorption, and adjustable energy levels. Despite their nonplanar geometry, which hinders charge transport, these acceptors have revealed remarkable photovoltaic performance through rational molecular design. The molecular design, the role of extending π-conjugation, and the use of a donor-acceptor approach are discussed which contributes to the development of efficient TCBD/DCNQ-bridged NFAs. This review highlights key examples of NFAs based on TCBD/DCNQ-bridged molecules and achieved power conversion efficiencies up to 9.29% in binary blends and 17.36% in ternary devices. By consolidating recent developments in this field, this review provides critical insights into their potential as NFAs while addressing current challenges and future opportunities for next-generation OSC applications.