enhance the bimolecular combination rates in perovskite emitters with good morphology. [24] Quasi-two-dimensional (quasi-2D) perovskites are one kind of promising branches to serve as highly efficient emitters for LEDs. Their low-dimensional phases inherently have larger E b (hundreds of meV) than the 3D counterpart. [25][26][27][28] One frequently used Ruddlesden-Popper (RP) low-dimensional perovskite presents in the formula of L 2 A n-1 B n X 3n+1 , [29][30][31] where L is the large-size organic cations such as butylammonium (BA + ) and phenethylammonium (PEA + ). The steric hindrance of these large-size cations separates the 3D structure into low-dimensional phases with several [PbBr 6 ] 4− layers, the number of which refers to the n value in the formula. [25] Consequently, a series of lowdimensional phases with various bandgaps are obtained from 2.44 eV (n = 5) to 2.67 eV (n = 3), 2.84 eV (n = 2), and 3.07 eV (n = 1). [32,33] It is worth mentioning that the main photoluminescence (PL) peak still emits from the 3D domains, demonstrating that these lowdimensional phases mainly act as an energy funnel to transport charge carriers to narrow bandgap domains rather than radioluminescence. [25,34] The energy funnel effect orientates the charge transport pathway, increasing the number of radiative recombination carriers. [30,35] Sun et al. reported CsPbBr 3 -based quasi-2D perovskite LEDs with an external quantum efficiency (EQE) of 15.5%. [9] The PL intensity and lifetime were dramatically improved upon the addition of 40 mol% phenethylammonium bromide (PEABr). You et al. deployed a strategy of controlling phase composition to reach a maximum EQE of 14.36%. [25] Concomitantly, the incorporation of PEABr greatly strengthened the film-forming properties. Thus, smooth and compact perovskite film was obtained, which was beneficial for the carrier injection in LED devices. However, there still remains two issues that inhibit the advancement of quasi-2D perovskite films for LEDs. On one hand, the formation of low-dimensional phases is unpredictable due to the random stacking of [PbBr 6 ] 4− sheets. [31] Upon carrier injection charges initially accumulate in small-n phases within ps scale. In this case, excessive small-n phases would hinder charge transport, resulting in insufficient exciton energy transfer toward large n phases (n ≥ 5), where radiative recombination takes place. On the other hand, the decrease of grain size implies the increase of Quasi-two-dimensional (quasi-2D) perovskite light-emitting diodes (PeLEDs) are considered as one of the most potential candidates in electroluminescence territory owing to their unique quantum confinement effect and excellent thermal stability of the light. Nevertheless, heterogeneous energy domain distribution leads to severe non-radiative recombination in the process of energy transfer, which enormously hinders the performance and application of PeLEDs. Herein, an ambipolar amino acid, 5-aminovaleric acid (5AVA), is demonstrated to be able to coordinate lead and halides simult...