Reduced Efficiency Roll-Off and Improved Stability of Mixed 2D/3D Perovskite Light Emitting Diodes by Balancing Charge Injection

Perovskite light emitting diodes (PeLEDs) have reached external quantum efficiencies (EQEs) over 21%. Their EQE, however, drops at increasing current densities (J) and their lifetime is still limited to just a few hours. The mechanisms leading to EQE roll-off and device instability require thorough investigation. Here, improvement in EQE, EQE roll-off, and lifetime of PeLEDs is demonstrated by tuning the balance of electron/hole transport into a mixed 2D/3D perovskite emissive layer. The mixed 2D/3D perovskite layer induces exciton confinement and beneficially influences the electron/hole distribution inside the perovskite layer. By tuning the electron injection to match the hole injection in such active layer, a nearly flat EQE for J = 0.1-200 mA cm(-2), a reduced EQE roll-off until J = 250 mA cm(-2), and a half-lifetime of approximate to 47 h at J = 10 mA cm(-2) is reached. A model is also proposed to explain these improvements that account for the spatial electron/hole distributions.