Leveraging isomeric effect of third components in D18:Y6 system to 18.51% efficiency

For ternary organic solar cells (TOSCs), the precise function of the third constituent and the underlying mechanisms is not fully deciphered. This complexity becomes more pronounced when the acceptor demonstrates an isomeric effect, a fairly prevalent occurrence. In addressing this complexity, an exploration into the isomeric impact of the third element could yield valuable insights into its behavior within the ternary configuration, potentially leading to the attainment of the highest achievable efficiency. Herein, two distinct isomers of the BTP-H2 molecule, named as BTP-H2-γ and BTP-H2-δ, were synthesized individually and subsequently incorporated into the D18:Y6 system. Impressively, resultant ternary devices displayed optimized yet diverse outcomes. Notably, the device founded on BTP-H2-γ exhibited a superior open-circuit voltage and power conversion efficiency of 18.51%, representing one of the most notable achievements within ternary systems built upon the D18:Y6 combination. Subsequent analyses unveiled that the favorable packing behavior observed in the BTP-H2-γ-based ternary device facilitated the charge transportation and improved morphology. These findings may elevate both the performance and reproducibility of TOSCs and advance our comprehension regarding the relationship between the structural attributes of the third component and its impact on the performance of the host system.