Researchers explore lead-free rare-earth-based double perovskite nanocrystals with near-infrared emission

A research group, led by Prof. Han Keli from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences (CAS), in collaboration with Prof. Miao Xiangyang's group from Shanxi Normal University, recently explored the colloidal synthesis of all-inorganic rare-earth-based double perovskite NCs with NIR emission, and revealed their exciton dynamics.

Previous studies mainly focused on the photoluminescence (PL) in the visible region, and those on the near-infrared (NIR) PL of lead-free perovskite NCs are rare.

The researchers synthesized all-inorganic rare-earth-based Cs₂NaEr_1-xB_xCl₆ (B: In, Sb, Bi; x = 0, 0.13, 0.5) double perovskite NCs by hot injection with variable temperature.

They found that all these NCs exhibited a NIR PL emission from ⁴I13/2 ' ⁴I15/2 transition of Er³⁺, and on account of the incorporated Sb³⁺, Cs₂NaEr_0.5Sb_0.5Cl₆ NCs showed a 23-fold NIR PL enhancement with the average lifetime of 119.1 μs.

"The origin of NIR PL enhancement was attributed to the increase of exciton absorption, the longer PL lifetime, the suitable phonon-assisted process caused by the indirect band structure, and the process of long-lived dark trap state assisted NIR PL emission," said Prof. Han.