UCLA

All-inorganic perovskites have attracted tremendous interest for their tunable optical properties and remarkable stability when compared with its hybrid counterpart. Although considerable efforts have been devoted to synthesizing micro-crystalline domains and various nanostructures, it remains a considerable challenge to produce high-quality monocrystalline thin films that are indispensable for functional electronics and optoelectronics. Furthermore, due to the fragility of metal halide perovskites, it remains a standing challenge to use conventional lithography to create reliable electrical contacts, rendering the intrinsic electrical transport properties of such perovskite materials are often seriously convoluted/plagued by poor electrical contacts. Starting from the vapor phase deposition of cesium lead halide CsPbX3 (X=Cl, Br, I) microplates, we demonstrated the growth of large-area monocrystalline all-inorganic perovskite thin films on muscovite mica. We show highly oriented CsPbBr3 square microplates can be readily grown on the (001) surface of muscovite with an epitaxial relationship of CsPbBr3-(001) paralleled to muscovite-(001), CsPbBr3-[100] paralleled to muscovite-[100] and CsPbBr3-[010] paralleled to muscovite-[010], which eventually merge together to form a continuous monocrystalline thin film. Time resolved photoluminescence (TRPL) decay measurements give a carrier lifetime of 170 ns, considerably longer than that in spin-coated thin films and well comparable to that in the highest quality bulk crystals. Aiming to resolve the problem of poor electrical contacts, we have further developed a simple physical transfer approach to create high-quality van der Waals (vdW) contacts, where the prefabricated thin film gold electrodes are directly laminated onto the perovskite thin films with minimum interfacial damage to produce electrical contacts for functional devices. The electrical and photoelectrical transport studies demonstrated an extraordinary photocurrent gain exceeding 106. The van der Waals contacts enable not only accurate measurements at room temperature but also the exploration of electrical properties at cryogenic conditions. A record-high carrier mobility exceeding 2,000 cm2/Vs has been achieved at 80 K and a quantum interference induced weak localization behavior in halide perovskite materials with a coherence length up to 49 nm has also been revealed for the first time by magnetotransport studies at 3.5 K. The growth of large-area high-quality perovskite thin films and the integration of the damage-free metal integration approach mark important steps for both the fundamental investigation and potential applications of the perovskite materials in integrated optoelectronics.