Mixed Ruddlesden-Popper and Dion-Jacobson Phase Perovskites for Stable and Efficient Blue Perovskite LEDs

Producing efficient blue and deep blue perovskite LEDs (PeLEDs) still represents a significant challenge in optoelectronics. Blue PeLEDs still have problems relating to color, luminance, and structural and electrical stability so new materials are needed to achieve better performance. Recent reports suggest using low n states (n = 1, 2, 3) to achieve blue electroluminescence in quasi-2D Ruddlesden-Popper (RP) perovskite films. However, there are fewer reports on the other quasi-2D structure, Dion-Jacobson (DJ) perovskites, despite their highly desirable optical properties, due to the difficulty in achieving charge injection. To resolve this issue, here we have mixed DJ phase precursors, propane-1,3-diammonium (PDA) bromide into RP phase perovskites and fabricated low-dimensional PeLEDs. It was found that these specific precursors aid in suppressing both the low n (n = 1) and high n (n ≥ 4) quasi-2D RP phases and is an effective strategy in blue-shifting sky-blue RP perovskites into the sub-470 nm region. With optimization of the PDA concentration and device layers, we achieved an EQE of 1.5% at 469 nm and stable electroluminescence (EL) for the first deep blue PeLED to be reported using DJ perovskites.