Efficient and tunable nanoscale light emitters with improved resistance!

Lead halide perovskites (LHPs) with composition CsPbX3 (X a halide, such as I, Cl, Br) have attracted intensive focus from the scientific community due to technological advances in the areas of photovoltaics, LEDs, radiation detection, and thermometry. A key limit for their application is their long-term stability and production with the required crystal structure, which tunes their electronic and optical behavior.

Recently, Jingwei Hou (Univ. of Queensland, UQ, Australia) and collaborators report on a new class of composites, comprised of LHPs nanoparticles embedded and protected by metal organic frameworks (MOFs). These compounds were produced by liquid phase sintering performed under temperature conditions where solid grans of LHPs and MOFs coexist with a wetting liquid, followed by fast solidification in liquid nitrogen. This lead to the reliable production of tens-of-nanometers LHPs crystals dispersed (and protected) in the MOF with efficient light emission and wavelength control (halide element substitution). This discovery is a significant advance in perovskite nanocrystal technology. Previously, these nanocrystals had to be produced exclusively in the bone-dry atmosphere of a laboratory, as the perovskites themselves are extremely sensitive to ambient conditions, including exposure to air, moisture, and light. In addition to easier manufacturing, the protection by the MOF ensure long-term stability and remarkable mechanical properties, opening up the way for future applications in screen technologies. The findings will enable the manufacture of glass screens that show improved mechanical strength but also deliver crystal clear image quality. This work is published in Science.

This work is a collaboration lead by Dr. Jingwei Hou and Prof. Lianzhou Wang (UQ), Prof. Thomas D. Bennet (U. of Cambridge, UK), and Prof. Sean M. Collins (U. of Leeds, UK), including physicists of Laboratoire de Physique des Solides (LPS). The production of these new composites and the understanding of their properties was only possible through the combination of experimental technique from all partners. First, the composites were designed and produced at the UQ and characterized by macroscopic methods to identify the presence of perovskites in the MOFs, their global emission spectrum and their quantum efficiency using photoluminescence (Figure, upper left). Then, microscopic measurements were used in the UK to identify and confirm the nanometric CsPbX3 crystals in the MOF (Figure, upper right). Finally, catholuminescence was used at LPS in a scanning transmission electron microscope (ChromaTEM of the TEMPOS project) to prove light indeed was emitted by individual nanometer scale crystals (Figure lower part)

Figure. Hybrid lead halid perovskites and metal-organic framework composites show remarkable stability and light emission efficiency (upper left). Nanoscale electron diffraction in a Scanning Transmission Electron Microscope (STEM) allows one to identify the phase of individual CsPbX3 nanocrystals (upper right). Finally, cathodoluminescence (CL, bottom) on a STEM demonstrates that light stems from individual nanocrystals, all with very similar emission spectrum.

Liquid-phase sintering of lead halide perovskites and metal-organic framework glasses
J. Hou, P. Chen, A. Shukla, A. Krajnc, T. Wang, X. Li, R. Doasa, L. H. G. Tizei, et al.
Science, 2021, 374, 621-625
doi: 10.1126/science.abf4460

Luiz Galvao-Tizei