A twisted double donor in donor–acceptor–donor D2–D1–A–D1–D2 type emitters yields multicomponent charge-transfer emission

Abstract

Complex donor arms in thermally-activated delay fluorescence (TADF) molecules can potentially provide additional options for charge-transfer (CT) emission through higher twisting disorder, leading to broader emission spectra. Here we design novel TADF emitters with double twisted donor moieties and show that a structural complication of the carbazole-based donor arms by changing the molecular structure from D–A–D to D₂–D₁–A–D₁–D₂ yields a transition from a dual to a triple emission band with an additional CT emission component, providing a corresponding red shift and increasing low-energy emission contribution. The revealed relationship between increased complexity of the donor moiety and the multicomponent CT emission band in the D–A–D structures provides a clue for design of TADF emitters with extended emission spectra.