Henan University researchers have developed lanthanide-based, lead-free double perovskite nanocrystals that combine ultra‑narrow green emission with record‑high efficiency and excellent stability, targeting next‑generation high‑definition displays and scintillators.
The key challenge they address is that while lead halide perovskite nanocrystals offer excellent PLQY and narrow emission, their toxicity and poor environmental stability are serious drawbacks, and most lead‑free double perovskites either have broad self‑trapped‑exciton emission with low PLQY or, in the lanthanide‑based case, very weak absorption which limits practical brightness.
To solve this, the team synthesized Cs₂NaTbCl₆ double perovskite nanocrystals using a dual‑injection method, obtaining phase‑pure NCs with ultra‑narrow green emission (FWHM ≈ 10 nm). They then co‑doped the Cs₂NaTbCl₆ host with Sb³⁺ and Ce³⁺, exploiting the high defect tolerance of the perovskite lattice to introduce strongly absorbing sensitizer ions without degrading the crystal quality.
This co‑doping strategy broadens the excitation spectrum and greatly increases the absorption cross‑section, enabling efficient energy transfer from Sb³⁺/Ce³⁺ “antennae” to Tb³⁺ emitters and boosting the photoluminescence quantum yield to 99%, a near‑unity value reported as a record for lead‑free halide perovskite nanocrystals.
The researchers also demonstrate that these nanocrystals can be processed into large‑area (about 4.5 × 4.5π cm²) fluorescent films with uniform, bright green emission, and that the films function effectively as X‑ray scintillators, showing stable green luminescence with intensity that increases linearly with radiation dose.
Crucially, the nanocrystals retain almost their full luminescent intensity after more than one year of storage in ambient air, highlighting exceptional long‑term stability compared with typical lead perovskite NCs.
For commercial perovskite‑based technologies, this work shows that carefully doped, lead‑free double perovskite nanocrystals can deliver near‑unity PLQY, ultra‑narrow emission, scalable film fabrication, X‑ray scintillation, and good stability, bringing practical, environmentally friendlier perovskite emitters for displays and related optoelectronic applications significantly closer to reality.
