Phenazine-based non-fused electron acceptors for high-performance organic solar cells

Abstract

Excellent low-cost non-fused ring electron acceptors (NFREAs) are important for future large-scale application of bulk heterojunction organic solar cells (BHJ OSCs). In this work, a series of NFREAs were designed based on a phenazine unit for the first time. Ten molecules with different alkyl chain, π-bridges, and terminal halogenation were obtained and applied to BHJ OSCs. Various properties of FQ-4F, FQ-FCl, and FQ-4Cl were investigated in detail, due to their superior photovoltaic performance. Their optical properties, charge transport, and film morphology were regulated by controlling the degree of multi-chlorination. The three compounds exhibit near-infrared absorption, suitable energy levels, high stability, and good intermolecular stacking. As demonstrated by space-charge-limited currents, charge extraction and recombination, and contact angle and atomic force microscopy (AFM) measurements, FQ-4Cl exhibits higher and better balanced carrier mobility, improved exciton dissociation efficiency, and suitable phase separability. OSCs based on PM6:FQ-4Cl achieved a power conversion efficiency (PCE) of 10.11%, indicating that the construction of NFREAs with phenazine is a promising strategy.