Properties of electronically excited states of four squaraine dyes and their complexes with fullerene C70: A theoretical investigation

From visualizing the isosurfaces of hole and electron distributions of the lowest three excited states of four SQ-C70 complexes, it appears that excited states 1 of 1-C70, 1 of 2-C70, 2 of 3-C70 and 2 of 4-C70 have no evident spatial separation between hole and electron, distinctly exhibiting both hole and electron are localized on the SQ region without perturbation from C70 region. On the contrary, in excited states 2 of 1-C70, 2 of 2-C70, 3 of 3-C70 and 3 of 4-C70, both hole and electron are localized on the C70 region. Undoubtedly 3 of 1-C70, 3 of 2-C70, 1 of 3-C70 and 1 of 4-C70 are typical CT transition states, corresponding to charge transfer from SQ region to C70 region.171