Metal Organic Chemical Vapor Deposition for Chemically Precise Hybrid Perovskite Materials

NON-TECHNICAL SUMMARYThe growth of semiconductor materials from the vapor phase has, over the last several decades, permitted the development of advanced technologies including light-emitting diodes (LEDs) and lasers, among others. More recently, a new class of semiconductor material termed hybrid perovskites has emerged with a unique set of tunable properties, including the wavelengths of light that they absorb and wavelengths of light that they emit. Moreover, they exhibit unique electronic properties that can make them suitable for a variety of technologies, including solar cells, LEDs, lasers, etc. In this project, supported by the Solid State and Materials Chemistry program in the Division of Materials Research at the NSF, a new method to grow hybrid perovskite materials from the vapor phase will be developed. The method—termed metal organic chemical vapor (MOCVD)—has been widely used for other semiconductor materials but has yet to be developed for hybrid perovskites. A new, custom-built experimental apparatus will permit development of this MOCVD process. The system will allow direct control over each of the chemical constituents of the material to precisely modulate its chemical composition. The fundamental mechanisms of the growth process will be explored, and the ability to grow a variety of distinct hybrid perovskite materials will be tested. The results of this project are expected to elucidate fundamental principles underpinning the design of MOCVD processes for hybrid perovskite systems, enabling new technological devices to be explored in the long-term.TECHNICAL SUMMARYMetal organic chemical vapor deposition (MOCVD) is a widely used vapor-based method to grow solid-state materials, and it has become a particularly powerful technique for III-V semiconductors. Here, the vapor-phase synthesis of hybrid perovskite materials will be developed using a home-built MOCVD system that facilitates the precise flow of organo-lead, amine, and hydrogen halide precursors at a controlled pressure through a reactor with multiple temperature zones outfitted with in situ measurement capabilities that include optical extinction measurements, optical microscopy, and quartz crystal microbalance quantification of mass change. A broad set of amine and halide precursors will be utilized to probe the MOCVD synthesis of three-dimensional, two-dimensional (2D), and quasi-2D hybrid perovskite materials to prove the generality of the process, develop an understanding of the reaction chemistry, and synthesize complex heterostructures and superlattices. The proposal goals include: (1) to understand the vapor-phase and surface mediated reaction mechanisms that control the MOCVD deposition; (2) to synthesize specific hybrid perovskite compositions and phases including 3D materials, 2D layered materials, quasi-2D Ruddlesden-Popper phases and Dion-Jacobson phases; and (3) to develop microstructural control of grain size distribution and crystallographic orientation via the substrate and substrate functionalization. The research efforts will involve students in a project that bridges the interface between solid-state materials chemistry, physical chemistry, and chemical engineering, providing a breadth of experience that ranges from synthesis and mechanistic studies to instrument design/construction and solid-state characterization. Results will be disseminated through publications in high-impact journals as well as presentations at national conferences. In addition, the students and PI will be engaged in a broad set of outreach efforts, including demonstrations in elementary schools and an annual public science exposition.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.