Diketopyrrolopyrrole-based oligomers accessed via sequential CH activated coupling for fullerene-free organic photovoltaics

• Sequential activation of CH bonds for accessing complicate multi-DPP-based oligomers.
• The integration of easily accessible acceptors with economical donor for fullerene-free OPVs.
• High VOC of fullerene-free OPVs using P3HT as donor.
• Accessing renewable solar energy via sustainable chemistry.

Exploring sustainable chemistry for renewable energy plays a key role in meeting the ever increasing energy demand without sacrificing the environment. In this study, two novel diketopyrrolopyrrol(DPP)-based π-conjugated oligomers (named as TPE-DPP4 and BP-DPP4) have been readily synthesized via a ligand-free Pd-catalyzed sequential activation of CH bond in two steps with good yields starting from simple building blocks. Poly(3-hexylthiophene) is employed as an electron donor to blend with the new DPP-derived electron acceptors for the fullerene-free bulk heterojunction organic photovoltaics. The power conversion efficiency of 2.49% has been achieved, corresponding with an open-circuit voltage of 1.16 V, which is among the highest open-circuit voltages for the single-junction organic photovoltaics. The facilely accessible electron acceptors blended with cost-effective poly(3-hexylthiophene) donor for fullerene-free organic photovoltaics opens a new pathway to access renewable solar energy via sustainable chemistry.

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