Aggregation-induced emission luminogens (AIEgens) have been regarded as one of the significant prospects for organic light-emitting diodes, sensors, biological therapies, etc. owing to their intense emission in aggregated states. The expanded π-conjugated molecule conformations supposedly acquire the emission with a lower energy, however the optical performance of AIEgens in aggregated states defies this empirical assumption. The unexpected photophysical characteristics of AIEgens make it more challenging to design molecular conformations. Herein, to unveil the crucial factors dominating the optical performance of AIEgens, a series of diphenyldibenzofulvene (DPDBF) derivatives in crystals are utilized. We revealed that the emission energy of DPDBF derivatives in crystals is attributed to the tight connection with the conformation of the planar π-conjugated segment, but not the conformation torsion of phenyl blades or the intermolecular coupling, after systematically analyzing the impact factors, including molecular conformation parameters and intermolecular coupling, and further proved with the calculation results. Although the energy gap between the HOMO and LUMO is somewhat reduced by the expanded π-conjugated molecular conformation of the aforementioned DPDBF derivatives, the Stokes shift effect, which is primarily influenced by the conformation of the planar π-conjugated moiety, can realize to adjust the emission energy in a much more effective manner.