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Why Do Lead-Free Perovskite LEDs Gradually Dim?
Materials ScienceStandardAbout 3 min
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You might have noticed that some cheap LED bulbs become dimmer or flicker after long use. Scientists face a similar problem, but with more advanced "perovskite LEDs." These LEDs could replace traditional lead-based LEDs because they are lead-free and more environmentally friendly. However, scientists found that "tin-based perovskite LEDs," which use tin instead of lead, have a big problem: their light output decays quickly, and their lifetime is short. Why is that?
A research team from Xiamen University and Fudan University decided to investigate. They carefully observed what happened inside the LED when it was emitting light. They focused on a tin-based perovskite material called CsSnI₃. They found that when the LED was turned on, the tin ions changed from a "divalent" to a "tetravalent" state, which is an oxidation reaction. They also observed that this oxidation changed the crystal structure of the material, leading to reduced light emission.
Scientists explain that LEDs emit light when electrons and holes (positive charges) combine in the material. But in tin-based perovskites, the injection of electrons and holes is unbalanced, causing some tin ions to lose electrons and undergo "electrochemical oxidation." This oxidation is irreversible, like rusting iron. Once it happens, the material is damaged, and the LED gradually dims.
The team proposed a "synergistic strategy": adding other elements to the crystal lattice (lattice doping) to make it more stable, and adding a protective layer on the surface (surface passivation) to reduce oxidation. With this method, they successfully made efficient tin-based perovskite LEDs with a peak external quantum efficiency of 21.2% and a working lifetime of over 900 hours. This is much better than previous tin-based LEDs, but still behind traditional lead-based LEDs.
Although this research made progress, scientists are not sure if this strategy can make tin-based LEDs last long enough for practical use. Also, problems like tin ions being easily oxidized and difficulty controlling crystallization still need more research. So, this is just the first step, and there is a long way to go.
To understand this article, you need to know two concepts: 1. External Quantum Efficiency (EQE): This is a measure of how efficiently an LED converts electrical energy into light. Simply put, a higher EQE means the LED is more energy-efficient and brighter. An EQE of 21.2% indicates that a significant portion of electrical energy is successfully converted into light, but the actual definition is more rigorous, involving the ratio of photons to electrons. 2. Oxidation reaction: This is a chemical reaction where a substance loses electrons. For example, iron rusting is oxidation. In tin-based perovskites, tin ions lose electrons to become a higher valence state, which damages the material structure and reduces light emission.
Did you know? Tin-based perovskite LEDs emit near-infrared light, which is invisible to the human eye but can be used in optical communication and night-vision devices.
This article was researched and written from the following materials:
Primary research: ScienceOpen link
News report: IT之家29 August 2026Read the original
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