Effect of Precursor Composition on Ion Migration in Hybrid Perovskite CH3NH3PbI3 (original) (raw)
IEEE Electron Device Letters
Abstract
We used thin-film transistors (TFTs) to understand the effect of precursor composition on ion migration in the hybrid perovskite CH<sub>3</sub>NH<sub>3</sub>PbI<sub>3</sub>(MAPbI<sub>3</sub>). For all the precursor compositions we investigated (i.e. MAI/PbI<sub>2</sub> ratios of 0.5, 0.8, 1.0, and 1.2), the TFTs exhibited anomalous hysteresis in their current-voltage (I-V) characteristics, indicating mixed ionic-electronic conduction. The hysteresis in the TFTs with MAI/PbI<sub>2</sub> = 0.5 was the largest, followed by that of the TFTs with ratios of 1.2, 1.0, and 0.8. Although residual PbI<sub>2</sub> was the source of hysteresis in the PbI<sub>2</sub>-rich TFTs (MAI/PbI<sub>2</sub> = 0.5), we conclude that it may enhance electronic conduction and minimize ion migration when present in small amounts (as in the case of MAI/PbI<sub>2</sub> = 0.8). Ion vacancy defects in grain boundaries are pathways for ion migration and the PbI<sub>2</sub> residues passivate these defects, there by minimizing the vacancy-mediated migration of ions in the MAPbI<sub>3</sub>.
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