image: Figure | Synthesis of Cs/FA alloyed perovskite nanoplatelets for linearly polarized emission. a, In-situ photoluminescence spectra during the formation of each Cs/FA ratio of perovskite nanoplatelets (PeNPLs) in colloidal solution. Inset are photographs of colloidal PeNPL solutions illuminated with a UV lamp (365 nm wavelength). The Cs/FA ratio regulates the nucleation and growth kinetics, which influences the extent of nanoplatelet overgrowth and size distribution of PeNPLs. b, Schematic illustration of the synthesis of PeNPLs with tunable Cs/FA ratios. FA incorporation stabilizes the photoactive perovskite phase compared to Cs-only PeNPLs. Nevertheless, when the Cs/FA ratio deviates from the optimal range, heterogeneous growth can induce disordered PeNPLs. c, Polarization dependence of the normalized PL intensity of each PeNPL films. The Cs/FA-alloyed PeNPLs exhibit a higher degree of linear polarization than the Cs-only PeNPLs, which is attributed to their well-oriented superlattice and enhanced optical properties.
Credit: Junzhi Ye et al.
Metal halide perovskites have emerged as leading candidates for next-generation optoelectronic materials owing to their remarkable optical tunability and processability. However, achieving phase-stable and morphologically uniform iodide-based perovskite nanoplatelets (PeNPLs) has remained a major challenge due to thermodynamic instability and ligand detachment under ambient conditions.
In a new paper published in Light: Science & Applications, a team of scientists, led by Professor Robert L. Z. Hoye, Dr. Junzhi Ye and Dr. Woo Hyeon Jeong from the Inorganic Chemistry Laboratory, University of Oxford, along with Professor Bo Ram Lee from School of Advanced Materials Science and Engineering, Sungkyunkwan University in South Korea, and co-workers have report a formamidinium (FA)-alloying strategy that enhances the stability of CsPbI3 PeNPLs. FA incorporation not only improves the bulk thermodynamic stability to suppress degradation to the non-photoactive yellow phase, it also strengthens surface ligand binding, thus reducing environmental degradation. Through compositional engineering, the Cs/FA-alloyed PeNPLs self-assemble into highly oriented superlattices with improved vertical orientation, thus improving the degree of linear polarization of light emitted.
This integrated approach of compositional tuning and surface modulation demonstrates a practical route for stabilizing strongly confined PeNPLs while maintaining excellent optical anisotropy. The findings not only address the long-term stability bottleneck of red-emitting iodide-based PeNPLs but also pave the way for the realization of efficient and polarized light-emitting devices and next-generation photonic displays.
Journal
Light Science & Applications
Article Title
Enhanced stability and linearly polarized emission from CsPbI3 perovskite nanoplatelets through A-site cation engineering