Boosted Charge-Carrier Transport in Triple-Cation Perovskites by Ultrasonic Vibration Post Treatment

Abstract

Ultrasonic vibration imposed on the substrate of a drying perovskite solution film has previously been proposed as a nearly annealing-free method to improve film quality and thus the photovoltaic performance for perovskite solar cells. However, an in-depth understanding of the underlying mechanism of the improved film quality via ultrasonic vibration is still lacking. In this work, the effects of substrate vibration post treatment on the carrier lifetime and mobility are studied in triple-cation perovskite films. With 80 s of annealing-free vibration, the perovskite film demonstrates much stronger photoluminescence intensity and much longer carrier lifetime up to 2.634 µs, 2 orders of magnitude longer than that of the thermal annealed films. Optical pump terahertz probe spectroscopy reveals that the charge-carrier mobility increases to 121 ± 44 cm2 V−1 s−1 when subjected to 80 s vibration followed by annealing. Such mobility is about 80 ± 40 cm2 V−1 s−1 higher than that of other polycrystalline organic–inorganic hybrid perovskite thin films of similar composition. The diffusion length is improved to nearly 1.5 times. The new understanding on the vibration-induced charge-carrier transport properties paves the way for the application of ultrasonic vibration toward the performance improvement of perovskite-based electronic devices.