To demonstrate the effects of intermolecular interactions and vibronic couplings, here we simulate the absorption and CD spectra of two trtramers with and without the inclusion of vibronic effect. Figure : The calculated pure electronic absorption and CD spectra of PDI-CN and PDI-F tetramers by TD-DFT (the black dashed line) as well as the mixed LE-CTE exciton model with and without the LE-CTE couplings (the orange and green lines), respectively. The vertical dashed lines represents the oscillator strength in absorption and the rotatory strength in ECD. Gaussian lineshape with FWHM of 806 and 968 cm -1 was employed, respectively.