The Intrinsic Role of the Fusion Mode and Electron‐Deficient Core in Fused‐Ring Electron Acceptors for Organic Photovoltaics

Abstract The A‐DA′D‐A fused‐ring electron acceptors with an angular fusion mode and electron‐deficient core has significantly boosted organic photovoltaic efficiency. Here, the intrinsic role of the peculiar structure is revealed by comparing representative A‐DA′D‐A acceptor Y6 with its A‐D‐A counterparts having different fusion modes. Owing to the more delocalized HOMO and deeper LUMO level, Y6 exhibits stronger and red‐shifted absorption relative to the linear and angular fused A‐D‐A acceptors, respectively. Moreover, the change from linear to angular fusion substantially reduces the electron‐vibration couplings, which is responsible for the faster exciton diffusion, exciton dissociation, and electron transport for Y6 than the linear fused A‐D‐A acceptor. Notably, the electron‐vibration coupling for exciton dissociation is further decreased by introducing the electron‐deficient core, thus contributing to the efficient charge generation under low driving forces in the Y6‐based devices.