Robust perovskite lattice for durable and efficient pure-red light-emitting diodes

Metal halide perovskite light-emitting diodes are rising as promising candidates for next-generation display technologies. The bromine-iodine mixed halide perovskites contribute to straightforward emitters for pure-red emission, however, suffering from limited electroluminescent durability and efficiency due to highly sensitive optical properties to the featured soft lattice. Here, we report robust perovskites by intrinsically reinforcing the lattice with synergistic rigid ring ammonium and dedicated electrostatic polymer. We reveal the mechanism of enhanced lattice stiffness by sequentially clarifying the rigid cation-induced high atomic packing factor and the electrostatic polymer-derived strong octahedral Coulomb force. The resultant perovskites exhibit more than 100% improvement in bulk modulus and over 75% decrease in bond angle fluctuation under a high electric field of 107 V m−1. The robust perovskite lattice strongly suppresses the electric field-induced lattice distortion and ion migration, and strengthens the carrier radiative recombination. Consequently, we demonstrate durable and efficient pure-red PeLEDs with a long lifetime of 343.3 h and a high external quantum efficiency of 31.3%. Moreover, we reveal good compatibility of this approach in boosting the blue and green device performances. Mixed-halide perovskites enable pure-red displays but suffer from poor durability and efficiency because their soft lattices distort. Zhou et al. stiffened the lattice with rigid ammonium rings and an electrostatic polymer, producing durable, efficient devices.