A recent article in Advanced Science reported a new method for incorporating lithium ions into CsPbBr3 nanocrystals. This approach aims to improve their electronic properties for use in applications such as white light-emitting diodes (WLEDs).
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Enhancing CsPbBr3 nanocrystals
Within the field of optoelectronics, there is a significant focus on enhancing the electronic properties of (CsPbBr3) nanocrystals (NCs).
CsPbBr3 nanocrystals have excellent photoluminescence quantum yield (PLQY), stability, and tunable optical properties. These properties make them promising candidates for light-emitting diodes (LEDs), lasers, and other optoelectronic devices. However, they have a relatively low electrical conductivity, which limits their practical application in high-performance devices.
To make them usable in high-performance devices, the charge transport within the nanocrystals needs to be enhanced while preserving their intrinsic optoelectronic qualities. To solve this problem, doping mechanisms, surface engineering, and heterostructure formation have been explored.
Lithium-ion (Li+) doping is an emerging mechanism that may be an effective way to fundamentally alter the electronic properties of CsPbBr3 NCs.
Lithium’s small ionic radius and high mobility make it a suitable candidate for doping. Doping can influence both lattice and surface chemistry, potentially increasing electrical conductivity and improving device performance.
The Current Study
This study used a novel hot-injection synthesis method to incorporate lithium ions into CsPbBr3 nanocrystals. The lithium bromide (LiBr) was introduced into the reaction mixture in varying ratios to control the degree of doping and surface modification.
The Li⁺ ions interacted with CsPbBr3in two ways: limited insertion into the crystal lattice and surface passivation through the formation of Li-metal alloy species. The synthesis method was optimized by adjusting the LiBr-to-PbBr₂ ratio to balance doping efficiency with nanocrystal stability.
The study used transmission electron microscopy (TEM) to confirm nanocrystal morphology and size distribution, X-ray diffraction (XRD) to examine lattice structure and phase purity, and energy-dispersive X-ray spectroscopy (EDX) for elemental analysis.
To understand the electronic structural changes, density functional theory (DFT) calculations were performed, analyzing the density of states (DOS) and partial DOS near the valence and conduction bands.
Electrical properties were evaluated through device fabrication, using bottom-contact configurations. Conductivity measurements showed significant improvements after lithium incorporation.
Photoluminescence (PL) measurements assessed quantum yield improvements, while electroluminescence and luminous efficiency tests demonstrated the practical benefits for LED applications.
The study also examined phase behavior during synthesis, focusing on the formation of heterostructures like Cs4PbBr6, which contributed to surface passivation.
Results and Discussion
The incorporation of lithium ions into CsPbBr3 nanocrystals resulted in significant modifications to their physical and electronic behavior. The hot-injection method successfully introduced Li+ primarily through surface passivation and lattice incorporation, inducing the formation of Li-metal alloy species. This led to a dramatic increase in electrical conductivity, up to 50 times higher than that of untouched CsPbBr3 nanocrystals.
The increase in electrical conductivity is attributed to several mechanisms. Firstly, Li+ induces the formation of alloy species (LiₘPbₙ), which effectively passivate surface defect states that typically trap charge carriers and reduce charge transport.
DFT calculations confirmed that Lithium doping also shifts the density of states toward the conduction band and reduces the bandgap, enabling easier charge injection and movement.
DoS analysis showed Li+ doping introduces new states near the Fermi level, which bridge the valence and conduction bands, mostly involving Pb p orbitals. This results in an increased density of free electrons and leads to enhanced electrical conductivity.
The formation of heterostructures like Cs4PbBr6, driven by LiBr hydrolysis, also contributes to phase stability and passivation. These heterostructures exhibit weaker interactions with Li+ ions and help to improve the overall optoelectronic properties.
Enhanced PLQY was also observed after LiBR hydrolysis, increasing from 50 % in undoped CsPbBr3 to 67 % with optimized lithium doping, preserving the high radiative efficiency while boosting charge transport.
The increased conductivity translated into better device performance; white LEDs formulated with Li+ doped nanocrystals showed luminous efficiencies exceeding those of undoped counterparts, with values reaching up to 112.5 lm/W—surpassing pure CsPbBr3 devices.
Conclusion
The research shows the transformative effects of lithium-ion doping on CsPbBr3 nanocrystals, creating more conductive, stable, and efficient materials suitable for next-generation devices. This study opens avenues for further research into tailored dopant strategies, alloy formation, and surface engineering within perovskite systems.
This work improves understanding of doping mechanisms and their impact on both structure and electronic properties. These insights support the development of more stable, higher-performing perovskite-based optoelectronic materials for applications in lighting, displays, and photovoltaics.
Journal Reference
Ge Z., et al. (2025). Boosting Electronic Properties of CsPbBr3 Nanocrystals via Lithium-Ion Doping and Surface Passivation for Enhanced Electrical Conductivity and Efficient White Light-Emitting Diodes. Advanced Science, DOI: 10.1002/advs.202417304, https://advanced.onlinelibrary.wiley.com/doi/10.1002/advs.202417304