Strong electron-ion coupling in gradient halide perovskite heterojunction

The electron-ion coupling in iontronics has great significance and potential for energy conversion and storage devices. However, it is a substantial challenge to integrate iontronics into all-solid-state semiconductor circuits and explore the electron-ion coupling in semiconductor devices. Here, by utilizing the organic-inorganic halide perovskite, we fabricate a planar heterojunction with a gradient distribution of halide anions. The diode-like halide migration was investigated by bias voltage induced asymmetric blue shift in photoluminescence spectrum. This pseudo-ionic diode behaviour was found to result from asymmetric charge injection characterized by I-V curves and gradient-halides-induced vacancy hopping indicated by energy dispersive spectroscopy (EDS). The planar gradient perovskite heterojunction provides a viable route for extending iontronic devices into the regime of all-solid-state semiconductors.