Tuning Exciton Dynamics and Energy Transfer in Ternary Organic Solar Cells Using Pyridine‐Flanked DPP Acceptors

This study reports the synthesis of three novel non‐fullerene acceptors (NFAs), LM‐F, LM‐T, and LM‐Se, featuring a diketopyrrolopyrrole (DPP) core flanked by pyridine units and connected to dicyanorhodanine terminals via different π‐bridging heterocycles: furan, thiophene, and selenophene. These NFAs exhibit an A2–D–A1–D–A2 molecular architecture and are synthesized through efficient methods. All compounds demonstrated good thermal stability, broad absorption in the visible range (550–800 nm), and suitable energy levels for organic solar cell (OSC) applications. Density functional theory (DFT) simulations revealed favorable dipole moments for exciton dissociation, especially in LM‐Se. Binary OSCs using D18 as donor achieved power conversion efficiencies (PCEs) of 10.23% (LM‐T), 12.25% (LM‐F), and 13.84% (LM‐Se), with LM‐Se showing superior performance due to broader absorption, lower exciton binding energy, and enhanced charge transport. Incorporating LM‐Se into a ternary blend with D18 and Y6 ((D18:LM‐Se:Y6 1:0.4:0.8) further improved the PCE to 17.53%, outperforming the binary D18:Y6 device (15.12%). This enhancement is attributed to improved exciton dissociation, balanced charge transport, reduced recombination, and efficient Förster resonance energy transfer (FRET). AFM and XRD analyses confirmed favorable morphology and molecular packing, contributing to reduced energy loss and enhanced photovoltaic performance.