(581a) Two-Dimensional Halide Perovskite Lateral Epitaxial Heterostructures

Atomically sharp epitaxial heterostructures based on oxide perovskites, III-V, II-VI, and transition metal dichalcogenides semiconductors form the foundation of modern electronics and optoelectronics. As an emerging family of tunable semiconductor materials with exceptional optical and electronic properties, halide perovskites are attractive for applications in next-generation solution-processed solar cells, LEDs, photo/radiation detectors, lasers, etc. The inherently soft crystal lattice allows for greater tolerance to lattice mismatch, making them promising for heterostructure formation and semiconductor integration. However, epitaxial growth of atomically sharp heterostructures of halide perovskites have not been achieved so far owing to two critical challenges. First, the fast intrinsic ion mobility in these materials leads to interdiffusion and large junction widths. Second, poor chemical stability in these materials leads to decomposition of prior layers during the fabrication of the subsequent layers. In fact, the facile ionic motion and poor stability are limiting the commercialization of any halide perovskite-based electronic devices. Therefore, understanding the origins of the instability and identifying effective approaches to suppress ion motion are of great significance and urgency. In this talk, I will present an effective strategy to substantially inhibit in-plane ion diffusion in two-dimensional (2D) halide perovskites via incorporation of rigid π-conjugated organic ligands. For the first time, we demonstrate highly stable and widely tunable lateral epitaxial heterostructures, multi-heterostructures, and superlattices of 2D halide perovskites via a solution-phase synthetic strategy. Near atomically sharp interfaces and epitaxial growth are revealed from low dose aberration-corrected high-resolution transmission electron microscopy characterizations. Molecular dynamics simulations reveal that the suppressed halide anion diffusivity is attributed to a combination of reduced heterostructure disorder and larger vacancy formation energies for 2D perovskites with conjugated ligands. These findings suggest critical fundamental insights regarding the immobilization and stabilization of halide perovskite semiconductor materials and provide a new materials platform for complex and molecularly thin superlattices, devices, and integrated circuits.