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Creating a lead-free inorganic perovskite for broadband emission

Scientists from the Dalian Institute of Chemical Physics have produced photoluminescence materials as well as the processes that enable them to function. Credit: Ming Shi, Dalian Institute of Chemical Physics

Approximately one-fifth of worldwide power usage is accounted for by artificial lighting, making the development of efficient and stable luminescence materials vital to avoiding wasteful waste of electric energy. Single emitters with broad emission spectrums, such as lead halide perovskites, have recently attracted a great deal of attention for their potential use in artificial lighting and display technologies. Researchers in China focused on low-dimensional bismuth halide perovskites in order to generate lead-free and stable perovskites that emit a broad spectrum of light.

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They published their findings in the journal Energy Material Advances on April 15th.

In traditional mixed and multicomponent lights, there are many problems, such as the loss of efficiency caused by self-absorption, the complicated structure of the lights and their unstable colours because of different degradation rates of phosphors, that can’t be solved with single emitters with broad spectrum light. “The single emitters with broad spectrum light can solve these problems,” said paper author Rengui Li, a professor at the State Key Laboratory of Catalysis, Dalian National Laboratory for Clean Energy and Dalian Institute of Chemical Physics (CAS). “Because of their exceptional photoelectric characteristics, lead halide perovskites have emerged as very interesting next-generation optoelectronic materials for light-emitting applications.”

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It has been explained by Li that the study on broadband emission has been dominated by low-dimensional organic-inorganic hybrid lead halide perovskites, which benefit from their high electron-phonon coupling interactions, which result in the formation of self-trapped excitons.

“However, the toxicity of lead, as well as the intrinsic instability generated by organic cations, prevent their further commercial implementation,” Li explained. ” Consequently, the development of inorganic lead-free halide perovskites with high-efficiency broadband emission is critical.

Bismuth-based halide perovskites have received a great deal of attention in the optoelectronic sector because of their low toxicity, excellent chemical stability, and isoelectronic arrangement of Bi3+ with Pb2+, among other characteristics. According to Li, the Cs3Bi2Br9 has emerged as a promising emitter for light-emitting applications because of its high exciton binding energy, which allows it to efficiently promote exciton recombination. However, only a few reports on Cs3Bi2Br9 for broadband light emission at room temperature and pressure have been published, despite the fact that the low electronic dimensionality and strong quantum confinement brought about by the vacancy-ordered layered structure give it this potential to emit light in a broad spectrum.

The fact that Cs3Bi2Br9 has extremely strong exciton-phonon coupling as a result of its localised and compressed microstructure, according to Li, can result in self-trapped excitons responsible for the broad photoluminescence band being more susceptible to thermal quenching through emitting phonons that are nonradiative, and as a result, Cs3Bi2Br9 only exhibits broadband emission at low temperatures and high pressure. Cs3Bi2Br9 has been the subject of research by Li and his team, which has worked to develop the broadband emission and, more crucially, to understand the luminescence process.

“In this research, we demonstrate that it is possible to insert a tiny amount of Sb (0.13 weight percent) into the Cs3Bi2Br9 crystal structure without affecting its long-range structure,” Li added. According to the researchers, the resulting Cs3Bi2Br9:Sb displays a notable broad-band emission as well as a significant increase in photoluminescence quantum yield (PLQY).

PLQY is increased due to the modulation of exciton recombination pathways by Sb inclusion, and the nonradiative recombination of self-trapped excitons is reduced, according to Li’s research findings.

Li said that the Cs3Bi2Br9:Sb has a very long structural and optical stability, which makes it possible for the material to be used for a long time. The self-trapped excitons at different energies make up the broad spectrum of light that comes out of the material.

Further information: Ming Shi et al, Tuning Exciton Recombination Pathways in Inorganic Bismuth-Based Perovskite for Broadband Emission, Energy Material Advances (2022). DOI: 10.34133/2022/9845942

Source: Beijing Institute of Technology

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