Confinement Effects of a Noble Gas Dimer Inside a Fullerene Cage: Can It Be Used as an Acceptor in a DSSC?

A detailed density functional theory investigation of He₂-encapsulated fullerene C₃₆ and C₄₀ has been presented here. When confinement takes place, He-He bond length shortens and a non-covalent type of interaction exists between two He atoms. Energy decomposition analysis shows that though an attractive interaction exists in free He₂, when it is confined inside the fullerenes, repulsive interaction is observed due to the presence of dominant repulsive energy term. Fullerene C₄₀, with greater size, makes the incorporation of He₂ much easier than C₃₆ as confirmed from the study of boundary crossing barrier. In addition, we have studied the possibility of using He₂-incorporated fullerene as acceptor material in dye-sensitized solar cell (DSSC). Based on the highest energy gap, He₂@C₄₀ and bare C₄₀ fullerenes are chosen for this purpose. Dye constructed with He₂@C₄₀ as an acceptor has the highest light-harvesting efficiency and correspondingly will possess the maximum short circuit current as compared to pure C₄₀ acceptor.