Device structure and optoelectronic performance of a near-infrared tin-based perovskite LED. [Photo/en.xmu.edu.cn]
A research team from Xiamen University (XMU), working with a team from Fudan University, has identified the key mechanism behind the decline in light emission from tin-based lead-free perovskite light-emitting diodes (PeLEDs) and developed a strategy to improve their efficiency and operating stability.
The findings, published in Science in a paper titled "High-efficiency, long-lived lead-free perovskite light-emitting diodes," provide a basis for designing high-performance lead-free perovskite optoelectronic devices.
The work, led by XMU Professor Xie Rongjun and Fudan University Professor Wang Lixin, combined lattice doping with surface passivation to stabilize the CsSnI₃ lattice, suppress nonradiative recombination, and balance carrier injection and transport.
The researchers found that excessive hole injection during operation triggers electrochemical oxidation of Sn²⁺ in CsSnI₃ perovskite films, causing an irreversible phase transition from CsSnI₃ to Cs₂SnI₆. The transition generates a high density of vacancies and pinhole defects, increasing nonradiative recombination and sharply reducing light-emission efficiency.
The resulting near-infrared tin-based PeLEDs achieved a peak external quantum efficiency of 21.2 percent at 963 nanometers and a maximum radiance of 195.8 watts per steradian per square meter. At an initial radiance of 7.1 watts per steradian per square meter, the devices had an operating half-lifetime of 920.5 hours.
Tin-based CsSnI₃ PeLEDs are considered promising for applications including optical communications, night-vision imaging, data storage, and biomedical detection because they combine low toxicity, solution processability, and low cost.
