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<p>Light-emitting diodes (LEDs) are solid-state light sources whose efficiency and performance are fundamentally determined by carrier dynamics in direct bandgap semiconductors. The emergence of high-performance GaN-based LEDs has enabled widespread applications in lighting, displays, and optoelectronics, while simultaneously exposing intrinsic physical limitations that continue to motivate intensive research. Understanding these limitations requires a unified treatment of materials properties, device physics, and recombination mechanisms. This review provides a comprehensive overview of the physical principles governing LED operation, with emphasis on the factors that limit optical efficiency across different material systems and device designs. Fundamental aspects of p–n junction operation, carrier injection, quasi-Fermi level separation, and recombination kinetics are first discussed to establish the physical basis of light emission. Radiative recombination is examined in competition with nonradiative processes, including Shockley–Read–Hall recombination associated with defects and Auger recombination that becomes significant at high carrier densities. The discussion then focuses on LED material platforms, particularly III–V nitride semiconductors, highlighting the roles of bandgap engineering, strain, polarization-induced electric fields, alloy inhomogeneity, and crystalline defects in shaping carrier confinement and recombination efficiency. Device architectures based on heterostructures and quantum wells are analyzed in terms of carrier localization, wavefunction overlap, and leakage mechanisms. Key efficiency descriptors, such as internal quantum efficiency and external quantum efficiency, are interpreted through their underlying microscopic origins, and the long-standing issue of efficiency droop is reviewed by comparing leading physical models with experimental observations. Optical extraction losses, thermal effects, and carrier overflow are addressed as interconnected phenomena that collectively constrain device performance. Finally, recent progress in micro-LEDs, nanostructured emitters, and emerging semiconductor materials is reviewed to illustrate how nanoscale control of materials and interfaces is redefining efficiency limits and expanding future application prospects.</p>

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Review: materials-driven efficiency limits in light-emitting diodes: defects, carrier dynamics, and structure–property relationships

  • 期刊论文

  • 发表日期：

    2026年3月18日

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  • Nazir Mustapha,
  • Mokhtar Hjiri

摘要

Light-emitting diodes (LEDs) are solid-state light sources whose efficiency and performance are fundamentally determined by carrier dynamics in direct bandgap semiconductors. The emergence of high-performance GaN-based LEDs has enabled widespread applications in lighting, displays, and optoelectronics, while simultaneously exposing intrinsic physical limitations that continue to motivate intensive research. Understanding these limitations requires a unified treatment of materials properties, device physics, and recombination mechanisms. This review provides a comprehensive overview of the physical principles governing LED operation, with emphasis on the factors that limit optical efficiency across different material systems and device designs. Fundamental aspects of p–n junction operation, carrier injection, quasi-Fermi level separation, and recombination kinetics are first discussed to establish the physical basis of light emission. Radiative recombination is examined in competition with nonradiative processes, including Shockley–Read–Hall recombination associated with defects and Auger recombination that becomes significant at high carrier densities. The discussion then focuses on LED material platforms, particularly III–V nitride semiconductors, highlighting the roles of bandgap engineering, strain, polarization-induced electric fields, alloy inhomogeneity, and crystalline defects in shaping carrier confinement and recombination efficiency. Device architectures based on heterostructures and quantum wells are analyzed in terms of carrier localization, wavefunction overlap, and leakage mechanisms. Key efficiency descriptors, such as internal quantum efficiency and external quantum efficiency, are interpreted through their underlying microscopic origins, and the long-standing issue of efficiency droop is reviewed by comparing leading physical models with experimental observations. Optical extraction losses, thermal effects, and carrier overflow are addressed as interconnected phenomena that collectively constrain device performance. Finally, recent progress in micro-LEDs, nanostructured emitters, and emerging semiconductor materials is reviewed to illustrate how nanoscale control of materials and interfaces is redefining efficiency limits and expanding future application prospects.