Halogen‐free solvent processed organic solar sub‐modules (≈55 cm2) with 14.70% efficiency by controlling the morphology of alkyl chain engineered polymer donor

Abstract Goals of high efficiency, morphological analysis, and the ability to produce organic solar cell (OSC) sub‐modules using halogen‐free solvents are demanding. In this study, a robust conjugated polymer with thienothiophene π‐spacer with pendant alkyl side chain (NapBDT‐C12) was synthesized and used to fabricate sub‐modules. Excellent efficiencies were demonstrated by a NapBDT‐C12 integrated ternary blend, which was used to produce stable small‐area‐to‐sub‐module devices using O‐xylene. The efficiency of the NapBDT‐C12 added small‐area ternary devices (PM6:NapBDT‐C12:L8‐BO) was 18.71%. Owing to the controlled homogeneity of the blend with favorable nanoscale film morphology, enhanced carrier mobilities, and exciton dissociation/splitting properties, contributed to the efficiencies of small‐area‐to‐sub‐module OSCs. Moreover, a 55 cm2 sub‐module with an efficiency of 14.69% was accomplished by bar coating using O‐xylene under ambient conditions. This study displays the potential of a ternary blend based OSC device to produce high efficiency scalable sub‐modules at ambient conditions.