Ternary blending and copolymerization strategies have proven advantageous in boosting the photovoltaic performance of organic solar cells. Here, 15% efficiency solar cells using copolymerization donors are demonstrated, where the electron-withdrawing unit, ester-substituted thiophene, is incorporated into a PBDB-TF polymer to downshift the molecular energy and broaden the absorption. Copolymer-based solar cells suitable for large-area devices can be fabricated by a blade-coating method from a nonhalogen and nonaromatic solvent mixture. Although ternary solar cells can achieve comparable efficiencies, they are not suitable for environment-friendly processing conditions and show relatively low photostability compared to copolymer-based devices. These results not only demonstrate high-efficiency organic photovoltaic cells via copolymerization strategies but also provide important insights into their applications in practical production.
Keywords: blade coating; copolymers; organic photovoltaic cells; photostability; power conversion efficiency.
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