A new approach to optimization of dye-sensitized solar cell, DSSC, performance, based on addition of POSS-based ionic liquid as an additive for I-/I-3(-) electrolyte systems is proposed. Iodide PEO-POSS Its are presented as conductive and thermally stable additives for DSSC electrolytes. Multifunctional M(EO)(n) Im(+)I(-) PIB7T8 POSS ILs with polyethylene oxide, PEO, chains of different lengths, n = 1-7 for M(PEG350), were synthesized, characterized and used as electrolyte additives for DSSCs, based on MPIm(+)I(-) or M(EO)(2)PIm(+)I(-)/butyronitrile electrolyte systems. The amphiphilic PEO ionic liquid-functionalized POSS molecules are considered as a potential POSS-based anodic surface modifier. The beneficial orientation of the PEO-POSS IL additive with the longest PEO chain at the anodic surface enabled a 7% increase in DSSC conversion efficiency. The positive influence of the additives' specific structure and anodic surface orientation on DSSC performance will be revealed in this research.