The emergence of Y6-type nonfullerene acceptors has greatly enhanced the power conversion efficiency (PCE) of organic solar cells (OSCs). However, which structural feature is responsible for the excellent photovoltaic performance is still under debate. In this study, two Y6-like acceptors BDOTP-1 and BDOTP-2 were designed. Different from previous Y6-type acceptors featuring an A-D-Aʹ-D-A structure, BDOTP-1, and BDOTP-2 have no electron-deficient Aʹ fragment in the core unit. Instead, there is an electron-rich dibenzodioxine fragment in the core. Although this modification leads to a marked change in the molecular dipole moment, electrostatic potential, frontier orbitals, and energy levels, BDOTP acceptors retain similar three-dimensional packing capability as Y6-type acceptors due to the similar banana-shaped molecular configuration. BDOTP acceptors show good performance in OSCs. High PCEs of up to 18.51% (certified 17.9%) are achieved. This study suggests that the banana-shaped configuration instead of the A-D-Aʹ-D-A structure is likely to be the determining factor in realizing high photovoltaic performance.

Ionic liquid 1-ethyl-3-methylimidazolium acetate ([EMIM][OAc]), 1butyl-3-methylimidazolium acetate ([BMIM][OAc]), and a mixture of [EMIM][OAc] and dimethyl sulfoxide (DMSO) were used as solvents to separate the maximum boiling azeotropic mixture of ethyl acetate and chloroform. The ternary vapor−liquid equilibrium (VLE) data of ethyl acetate + chloroform + [EMIM][OAc] were measured at 101.3 kPa. The liquid phase is partially soluble when the concentration of ethyl acetate and [EMIM][OAc] is high in the ternary system, and DMSO is employed to enhance the solubility of [EMIM][OAc] in ethyl acetate. Different entrainers were compared by measuring the VLE of ethyl acetate + chloroform + DMSO, ethyl acetate + chloroform + [BMIM][OAc], and ethyl acetate + chloroform + [EMIM][OAc] + DMSO at 101.3 kPa. All of the entrainers can improve the relative volatility of ethyl acetate to chloroform. The salting-out effects of the ILs [EMIM][OAc] and [BMIM][OAc] are significantly greater than that of DMSO. Organic solvent DMSO can enhance the selectivity of [EMIM][OAc] at high ethyl acetate concentration. The effects of the entrainers were analyzed by sigma-profiles. The nonrandom two-liquid (NRTL) activity coefficient model was adopted to correlate the experimental data. The binary interaction parameters of the NRTL equation were obtained, and the correlation results agreed well with experimental results.