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EP02.11.02 : Electronic Properties of Layered Organic Metal Halide Semiconductors

11:00 AM–11:30 AM Apr 5, 2018

PCC North, 200 Level, Room 222 BC

Description
Michael Chabinyc1

1, University of California, Santa Barbara, Santa Barbara, California, United States

Solution-processed materials have significant promise for thin film electronics ranging from solar cells to LEDs to transistors. Hybrid organic metal halides, such as CH3NH3PbI3, have garnered significant attention because they are earth-abundant, solution processable materials that can be used to form solar cells with high power conversion efficiency. We will present our work on elucidation of the optoelectronic properties of organic metal halide semiconductors with layered structures formed by replacement of halide ions by the pseudohalide thiocyanate (SCN-) and by the introduction of a mixed organic cations to form Ruddlesden-Popper structures. Using time-resolved microwave conductivity (TRMC) experiments, the carrier mobility in-plane in thiocyanate compounds was found to be relatively high and comparable to that of polycrystalline methylammonium lead iodide (MAPbI3) along with similar carrier lifetimes. In contrast, the layered Ruddlesden-Popper compounds, (CH3(CH2)3NH3)2(CH3NH3)n−1PbnI3n+1 (n = 1, 2, 3, 4), do not show lifetimes comparable to CH3NH3PbI3. Instead the observed behavior by TRMC is a complex function of the “perovskite” thickness (n) and the morphology of the thin films. We will present structural studies of polycrystalline thin films of the Ruddlesden-Popper compounds using X-ray scattering that help to address this difference in behavior. Measurements of the band tail of these materials using solar cells also reveal key insights into the electronic structure of spin coated films.

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