Recent advances in metal-halide perovskite light-emitting diodes (LEDs) have positioned them as a compelling alternative to conventional LED technologies, particularly due to their exceptional spectral tunability, compatibility with solution processing, and improved defect passivation strategies. These developments highlight the potential of perovskites to address limitations in traditional LED materials while enabling new applications in displays, lighting, and optoelectronics.

Spectral tunability is one of the most distinctive advantages of perovskite LEDs. Unlike conventional III-V semiconductors such as GaN or InGaN, which require precise compositional adjustments to achieve color variation, perovskites offer broad emission wavelength control through simple halide alloying. By varying the ratios of bromide, chloride, or iodide in the perovskite lattice, emission can be tuned across the entire visible spectrum, from deep blue to near-infrared. For example, mixed halide perovskites like CsPb(Br/I)3 exhibit continuous bandgap engineering, allowing precise control over electroluminescence peaks between 470 nm and 700 nm. This contrasts sharply with conventional LEDs, where achieving pure blue or red emission often demands complex multi-quantum-well structures or phosphor down-conversion layers. The narrow emission linewidths of perovskites, typically below 20 nm, further enhance color purity, a critical metric for high-definition displays.

Solution processing represents another key advantage of perovskite LEDs. Traditional LEDs rely on high-temperature epitaxial growth techniques such as metal-organic chemical vapor deposition (MOCVD), which are energy-intensive and require rigid substrates. In contrast, perovskite films can be deposited through low-cost, scalable methods like spin-coating, inkjet printing, or blade coating. Recent progress in precursor engineering has enabled the fabrication of high-quality perovskite layers at temperatures below 150°C, compatible with flexible plastic substrates. Additives such as polyethylene glycol or zwitterionic molecules have improved film uniformity, reducing pinhole defects that previously limited device performance. The ability to process perovskites in ambient conditions, albeit with controlled humidity, further differentiates them from conventional LEDs that necessitate ultra-high-vacuum environments.

Defect passivation has been a critical focus in enhancing the efficiency and operational stability of perovskite LEDs. While perovskites exhibit high defect tolerance compared to traditional semiconductors, non-radiative recombination at surface and grain boundary defects still limits performance. Recent strategies include the use of multifunctional passivators such as zwitterionic molecules, which simultaneously neutralize ionic defects and suppress halide migration. For instance, treatments with phenethylammonium halides have been shown to reduce trap densities by over an order of magnitude, leading to external quantum efficiencies (EQEs) exceeding 20% in green-emitting devices. Another approach involves dimensionality engineering, where 2D/3D heterostructures are formed to confine charge carriers and minimize interfacial losses. These advances contrast with conventional LEDs, where defect management primarily relies on costly lattice-matched epitaxial growth and sophisticated doping profiles.

The charge injection and transport dynamics in perovskite LEDs also differ significantly from conventional devices. In traditional LEDs, carrier injection is typically balanced through precise doping of p-type and n-type layers, often requiring complex heterostructures. Perovskites, however, exhibit ambipolar transport properties, simplifying device architectures. Recent work has demonstrated efficient LEDs using single-layer perovskites sandwiched between organic charge transport layers, reducing the need for doped semiconductors. Innovations in interfacial engineering, such as the incorporation of ultrathin polymer interlayers, have further improved charge balance and reduced leakage currents.

Operational lifetimes of perovskite LEDs have seen notable improvements, though they still lag behind mature technologies like organic LEDs (OLEDs) or inorganic LEDs. Encapsulation techniques borrowed from OLED research, such as atomic layer deposition of Al2O3 barriers, have extended device stability under continuous operation. While conventional LEDs boast lifetimes exceeding 50,000 hours, state-of-the-art perovskite LEDs now achieve several hundred hours at practical brightness levels (100 cd/m²). Accelerated aging tests suggest that further optimization of defect passivation and encapsulation could narrow this gap.

The unique optoelectronic properties of perovskites also enable novel device architectures. For example, perovskite LEDs can be engineered to exhibit directional emission patterns without additional optical outcoupling structures, a feature attributed to their high refractive index and thin-film interference effects. Recent demonstrations include ultra-thin (sub-100 nm) devices that maintain high EQEs, contrasting with conventional LEDs that often require thick buffer layers for strain relaxation. The compatibility of perovskites with plasmonic nanostructures has also opened avenues for enhanced light extraction and Purcell effect modulation, areas less explored in traditional LED systems.

Environmental considerations further differentiate perovskite LEDs from conventional technologies. The absence of rare-earth elements (e.g., indium in ITO electrodes) and the potential for lead-free compositions (e.g., tin-based perovskites) align with growing sustainability demands. Solution processing reduces energy consumption during manufacturing, whereas conventional LED production involves high-temperature epitaxy and toxic precursors like ammonia. However, challenges remain in scaling up perovskite synthesis while maintaining batch-to-batch reproducibility, an area where III-V semiconductor workflows excel.

In summary, metal-halide perovskite LEDs have made significant strides in spectral tunability, solution processability, and defect management, offering distinct advantages over conventional LED technologies. While challenges in long-term stability and large-scale manufacturing persist, recent advances underscore their potential to complement or even surpass existing optoelectronic platforms in specific applications. The ongoing refinement of material compositions, device architectures, and passivation strategies continues to push the boundaries of what is achievable with this versatile class of semiconductors.