A wide-bandgap π-conjugated polymer for high-performance ternary organic solar cells with an efficiency of 17.40%

Although substantial progress has been made at increasing power conversion efficiencies (PCEs) the field of ternary organic solar cells (TOSCs) during the past few years, choice of π-conjugated polymers that exhibit strong complementary spectra and achieve high photovoltaic parameters (open-circuit voltage (Voc), short-circuit current density (Jsc), fill factor (FF), and PCE) simultaneously is limited. In this paper, TOSCs demonstrated a high PCE of 17.09% based on a π-conjugated polymer (named SiCl-BDT, bandgap ≈ 1.84 eV) as a third component (15 wt%) to the host binary system consisting of a PM7:Y7. The third component was used to achieve enhanced absorption coefficient (λ_max = 5.5 × 10⁴ cm⁻¹) and more balanced charge carrier transport, frontier molecular orbital (FMO) energy levels, and blend miscibility, contributed to an improved FF of 70.38% and yielded an impressive Jsc of 27.37 mA/cm² and Voc of 0.84 V. The PCE was higher than the host PM7:Y7 (15.13%) binary device. In addition, we found the photovoltaic performance of TOSCs could be further increased to a benchmark PCE of 17.40% using an interface engineering strategy. Thus, enables efficient charge transfer in TOSCs compared with that of without interlayer TOSCs, leading to high Jsc, Voc. The resulting encapsulation-free TOSCs showed excellent ambient and thermal stability. Accordingly, this work suggests that the use of a passivated electron transporting layer (ETL) and a π-conjugated polymer as a third component offers a promising means of overcoming the lower PCEs of OSCs.