A multifunctional interface optimization strategy for efficient Quasi-2D blue perovskite Light-Emitting diodes

Domain distribution, defect density as well as carrier transport all exert some great impact on the performance of quasi-two-dimensional (quasi-2D) perovskites light emitting diodes (PeLEDs). Herein, the novelty multifunctional metformin hydrochloride (MFCl) buried passivated layer was introduced to optimize the crystal dynamics, surface morphology, and electro-luminescent properties of the quasi-2D perovskites. On the one hand, MF ion to some extent optimized the domain distribution just by both decreasing the n = 2 phase and increasing the three-dimensional (3D) phase, which facilitated the charge funnelling. On the other hand, by combining MFCl with PSS or PSS-Na, the energy level of the hole transport layer was effectively adjusted, resulting in an obvious reduction of the injection barrier. As a result, the MFCl-optimized blue quasi-2D PeLEDs with the maximum external quantum efficiency of 5.22 % was achieved, which is 3.6 times higher than that of the device without the MFCl treatment. This work provided favourable strategy for the performance enhancement of blue quasi-2D PeLEDs, in which a multifunction interface was introduced to synchronously improve the phase distribution as well as the defect passivation of quasi-2D perovskite, meanwhile all of those further promoted the charge transportation.