Materials Synthesis

Materials Synthesis

The primary focus of my group is design and synthesis of innovative hybrid solid-state semiconductors. We mainly focus on hybrid metal halides, including but not limited to halide perovskites. These cost-effective materials can be synthesized and processed using solution-based methods. Their structures integrate extended metal halide polyhedral frameworks with molecular organic cations. The polyhedra adopt various coordination environments, such as octahedral or tetrahedral configurations. The metals used include main group elements (e.g., Pb, Sn, In, Sb, Bi) and transition metals (e.g., Cu, Ag, Mn, Zn), while the halides consist of I, Br, and Cl. Organic cations serve as structural templates and introduce additional functionalities. With a vast selection of organic cations available, we employ a molecular design approach to fine-tune the structures, properties, and applications of these hybrid semiconductors.

One of the rockstar hybrid semiconductors is halide perovskites, which consist of six-coordinated octahedra connected by corner-sharing. They exhibit outstanding physical properties such strong absorption, long carrier lifetime and long diffusion length, which have led to their exceptional performances in optoelectronic devices. The major drawback of three-dimensional (3D) halide perovskites is their poor stability under moisture, heat and light. One of the solutions to this problem is to utilize lower-dimensional halide perovskites, which can be derived from 3D perovskites by slicing the octahedral layers in different directions and incorporating large organic cations called spacers. The hydrophobic organic cations create a protective "umbrella" layer, shielding the structure from environmental degradation.

When the shape and size of the spacer cations meet specific requirements, two-dimensional (2D) perovskites can be synthesized. Otherwise, one-dimensional (1D) or zero-dimensional (0D) structures would form instead. When the coordination environment of the structure is different from octahedral, they are referred to as “hybrid metal halides” rather than “halide perovskites”. We also want to move away from the toxic Pb to other main group elements and transition metals to explore their optical, electronic and magnetic properties.