To explain the origin of characteristic absorption peaks of two dimers, we analytically study the contributions of the LE and CT states to the low-energy adiabatic electronic excited states of the dimers. Consider a dimer AB, and assume that its two intramolecular LE states (A * B and AB * ) and two intermolecular CT states ( A + B -and A -B + ) determine the low-energy absorption of AB. For the sake of simplification, we further assume that the A and B molecules are identical, the To further show the effects of long-range excitation energy transfer and aggregation lengths in the electronic absorption spectra, we also display in Fig. the pure electronic absorption spectra of the DPND6 aggregate with 10 monomers and the DPND aggregate with 18 monomers. Here, the electronic-state properties are obtained from the model Hamiltonian constructed from the diabatic results of hexamer. The selected aggregation lengths are long enough to guarantee the electronic states not influenced by the boundary effects. As shown in Fig. (a), two dominate electronic states of the DPND6 aggregate with the great oscillator strengths in two different energy regions are both blue-shifted compared to those of dimer. In the DPND aggregate shown in Fig. (b), the low-energy electronic state is red-shifted whereas the high-energy one is blue-shifted. Moreover, it is quite remarkable that the relative oscillator strengths of low-energy and high-energy electronic states in the DPND aggregate are inverted, compared with the dimer system.