When LE and CTE states are coupled, significant changes appear on the spectra. Firstly, the spectra are red-shifted, and the intensity of the strongest absorption peak decreases, with new absorption peaks emerging in the higher energy region. Typically, high-energy CTE states are considered dark states; however, when the 10 high-energy CTE states couple with the 4 low-energy LE states, they can linearly recombine into 14 mixed exciton states. The high-energy excitons incorporate some components of LE states, enabling optical absorption through the LE states. According to the exciton composition analysis (Table ), the highenergy absorption peak in PDI-CN mainly originates from the eighth exciton state (22776 cm -1 ), which includes 15% LE state components. In contrast, the low-energy absorption peaks are primarily derived from the first (19775 cm -1 ) and fourth (21019 cm -1 ) exciton states, containing 87% and 82% LE components, respectively. In the ECD spectrum, the positive and negative peaks are mainly attributed to the rotatory strength contributions from the third and fourth exciton states, while the negative signal in the higher energy region is primarily due to the contributions of multiple exciton states.