Perovskite Light-Emitting Diodes: Engineering, Stability, and Applications.

Metal-halide perovskite light-emitting diodes (PeLEDs) have rapidly achieved external quantum efficiencies comparable to established organic and quantum-dot LEDs. Their narrow emission spectra, tunable bandgaps, high photoluminescence efficiencies, and low-temperature processing make them promising for displays, lighting, optical communication, and flexible electronics, although their commercialization remains limited by short operational lifetime, efficiency roll-off, unstable blue emission, ion migration, interfacial degradation, and poor large-area uniformity. This review provides a device-engineering-centered analysis connecting perovskite materials and processing conditions with charge injection, radiative recombination, optical extraction, and stability. It introduces the essential characteristics of 3D, 2D/quasi-2D, and nanocrystal perovskites and evaluates major engineering approaches, including composition and dimensionality control, crystallization regulation, defect passivation, transport-layer and interface modification, charge balancing, and optical outcoupling. An emphasis of this review is its comparison of the problems addressed by these approaches and their trade-offs among efficiency, spectral stability, lifetime, and manufacturing compatibility. Degradation under electrical operation is examined with attention to Joule heating, ion migration, charge accumulation, and interfacial reactions. Emerging patterned, reconfigurable, flexible, transparent, and communication devices are also discussed. Finally, the review identifies operational stability, efficient blue emission, scalable fabrication, high-resolution patterning, lead toxicity, and competition with OLEDs as the principal challenges for PeLED commercialization.