The history and development of Y6

Organic solar cells (OSCs) have developed progressively in efficiency over the last few years, benefitting from the emergence of non-fullerene acceptors (NFAs). Among kinds of non-fullerene acceptors, the recent A-DA'D-A (D: donor unit; A, A': acceptor unit) type acceptors have attracted considerable attention because of their ladder-type electron-deficient-core-based central fused backbone with improved transport properties and complementary absorption spectra to donors. In this Minireview, we present a brief history of the original design concepts and chemical development of A-DA'D-A type NFA molecules for OSCs and also provide a timeline that how the Y6 molecule in particular was progressively designed and synthesized in the Yingping Zou group.