Real-Time Electron and Hole Transport Dynamics in Halide Perovskite Nanowires

Lisa Janker, Yu Tong, Lakshminarayana Polavarapu, Jochen Feldmann, Alexander S. Urban, Hubert J. Krenner

Nano Letters 19 8701-8707 (2019) DOI: 10.1021/acs.nanolett.9b03396

For optoelectronic devices high transport mobilities of electrons and holes are desirable, which moreover should be close to identical. Acousto-optoelectric spectroscopy is employed to probe spatio-temporal dynamics of both electrons and holes inside CsPbI3 nanowires. These dynamics are induced without the need of electrical contacts simply by the piezoelectric field of a surface acoustic wave. Its radio frequency of  natively avoids spurious contributions from ion migration typically occurring in these materials. The observed dynamic modulation of the photoluminescence is faithfully reproduced by solving the drift and diffusion currents of electrons and holes induced by the surface acoustic wave. These calculations confirm that the mobilites of electrons and holes are equal and quantify them to be µeh=3±1cm2V-1s-1. Additionally, carrier loss due to surface recombination is shown to be largely suppressed in CsPbI3 nanowires. Both findings mark significant advantages over traditional compound semiconductors, in particular GaAs for applications in future optoelectronic and photovoltaic devices. The demonstrated sub-lifetime modulation of the optical emission may find direct application in switchable perovskite light emitting devices employing mature surface acoustic wave technology.