Ligand Engineering for Improving the Primary Color Emission Efficiency and Stability of Low-Dimensional Perovskites

Halide perovskites have raised wide interest these years for photovoltaics, light-emitting diodes, and other applications due to their excellent optical and electronic properties, low cost, solution processability, and diversity as a group of materials. By ligand designs, we will discuss the influences on the phase distribution, carrier transfer and confinement of low dimensional perovskites will be improved. Using blue quasi-2D perovskites LEDs (PeLEDs) as examples, we can enhance the hole injection for better balance carrier and improve the efficiency [1], we also modulate the n-phase distribution [2,3], optimize the carrier transfer and confinement [4] and suppress the ion migration [5] to improve PeLED performances. For perovskite nanocrystals (NCs), we will design the functional side-branches for good NC dispersion and high electrical conduction and then optimize the spacing between polydentate functional groups of polymer ligands to match the surface pattern of CsPbBr_1.8Cl_1.2 PeNCs, resulting in effective synergistic passivation effect and significant improvements in PeLED efficiency and stability [6-9]. We then further extend the ligand design to enhance the mechanical stability by establishing ligand-termination surface structure on perovskites with anchoring points and polymeric soft chains on perovskites beyond the corresponding functional group-only or polymer-only strategies in reducing the Young’s modulus to achieve high efficiency and mechanical stabile flexible PeLEDs [9]. Overall, the efficiency and stability of the red-green-blue (RGB) perovskite LEDs can be significantly improved by comprehensively designing the ligand structures.

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