Crystal orientation and insulating ligand of quasi-two dimensional perovskite optimized through silver ion doping for realizing efficient light emitting diodes

Quasi-two-dimensional lead halide perovskites (Q-2Ds) have outstanding optoelectronic properties and solution processability, and they have been widely studied as promising candidates for the development of low-cost and efficient LEDs. However, the disorderly crystal orientation and insulating ligand impair the performance of Q-2D based photoelectronic devices. Thus, a method based on silver (Ag) ion doping is formulated that provides a high dielectric constant, controls the crystal orientation, improves ionic balance, and successfully elevates the LED characteristics of these materials. With the addition of an appropriate amount of Ag+, the disorderly crystal orientation is inhibited, and defect passivation is achieved owing to improvements in photoluminescence quantum yield (PLQY) and carrier mobility. By contrast, the addition of excess Ag+ increases the possibility of the formation of AgBr during crystal growth, which aggravates the disorderly crystal orientation due to the destruction of ionic balance, which can be attributed to the strong affinity between Ag+ and Br-. Additionally, the hole-transport layer is modified upon Ag nanoparticle doping, which reduces luminescence quenching and hole injection barriers. Consequently, the luminance and external quantum efficiency of the optimized Ag+- doped Q-2D LED are 2 and 10 times higher, respectively, than those of the Q-2D LED without Ag+ doping.