Embedded Host/Guest Alloy Aggregations Enable High‐Performance Ternary Organic Photovoltaics

Abstract The ternary strategy has been intensively studied to improve the power conversion efficiencies of organic photovoltaics. Thereinto, the location of the guest component plays a critical role, but few reports have been devoted to this concern. Hereon, the distribution of LA1 as a guest acceptor in a variety of ternary scenarios is reported and the dominating driving forces of managing the guest distribution and operating modes are outlined. Governed by the appropriate relationship of compatibility, crystallinity, and surface energies between host and guest acceptors, as well as interfacial interactions between donor and dual acceptors, most of the LA1 molecules permeate into the internal of host acceptor phases, forming embedded host/guest alloy‐like aggregations. The characteristic distributions greatly optimize the morphologies, maximize energy transfer, and enhance exciton/charge behaviors. Particularly, PM6:IT‐4F:LA1 ternary cells afford high efficiency of 15.27% with impressive fill factors (FF) over 81%. The popularization studies further verify the superiority of the LA1‐involved alloy structures, and with the Y6‐family acceptor as the host component, an outstanding efficiency of 19.17% is received. The results highlight the importance of guest distribution in ternary systems and shed light on the governing factors of distributing the guests in ternary cells.