The formation of a middle-n phase is obstructed by a high formation energy for the Dion-Jacobson perovskites, leading to an energy transfer gap between the small-n phases and the light emission phase, which thus largely decreases the efficiencies of the related perovskite light-emitting diodes (PeLEDs). Herein, we report that the phase distribution is effectively modulated by the treatment of DMSO vapor, largely increasing the efficiencies of the relating PeLEDs to 13.7% and 15.5% with emission peaks at 489 and 494 nm, respectively. The rearranged phase distribution with matched energy landscape and phase content shows efficient energy transfer with an effectively eliminated energy transfer gap and significantly suppressed energy losses. This work puts forward an effective way of DMSO vapor treatment to modulate the phase crystallization and highlights the importance of reducing the energy losses in the energy transfer process, for the efficient light emission of Dion-Jacobson perovskites.