Highly oriented perovskites for efficient light-emitting diodes with balanced charge transport

Ruddlesden-Popper (RP) perovskites have attracted interests due to high performance in perovskite light-emitting diodes (PeLEDs). However, the insulating organic spacers decrease carrier mobility, and increase charge accumulation and non-radiative recombination losses, which significantly undermine device performance. Herein, by blending NH₃I(CH₂)₈NH₃I (ODA) and INH₃(CH₂)₂O(CH₂)₂O(CH₂)₂NH₃I (EDBE) large organic spacers into the precursor solution, we achieve preferential orientation of perovskite crystals perpendicular to the substrate with conductive channels across the two injecting electrodes. Consequently, effective charge injection and balanced charge transport are achieved, which is beneficial to increase radiation recombination. A low turn-on voltage of 1.4 V is achieved for mixture-1.5 perovskite (ODA: EDBE = 3:2, molar ratio) PeLEDs, and a maximum external quantum efficiency increases to 5.8% (EL peak ≈766 nm) at 2.0 V with a current density of 6.05 mA cm⁻² compared to that of the pure ODA (2.4%) and EDBE (1.1%) devices. The findings may spur new developments in charge injection and electron-hole balance for realizing efficient PeLEDs.