Author(s) Yu, X.; Yan, H.; Peng, Q.
Journal Langmuir
Date Published 2019 May 21

AlO atomic layer deposition (ALD), which uses trimethylaluminum (TMA) as the metal precursor, shows promise in improving the environmental stability of hybrid halide perovskites. However, it is not yet entirely clear how TMA, a strong Lewis acid, reacts with fresh perovskites and how the reaction affects the nucleation of ALD AlO. Here, the effects of reaction temperature and partial pressure of TMA on the mechanisms of TMA/CHNHPbI reactions are investigated. Our real time mass gain data and in situ mass spectrometry data show that the TMA/CHNHPbI reaction can either remove mass or accumulate mass onto CHNHPbI substrates, depending strongly on the reaction temperature and partial pressure of TMA. The TMA/CHNHPbI reaction probably generates TMA-CHNHx adduct compounds, which protects CHNHPbI from TMA by forming a shell at 25 °C in the vacuum process. However, these adduct compounds decompose at higher temperatures (e.g., 75 °C). This product layer is much thicker than a monolayer, suggesting the interface formed between AlO coating and CHNHPbI is blurring and messy. These results have not yet, but should be, carefully considered to correctly interpret the effect of ALD AlO treatment on optoelectronic properties of CHNHPbI.

DOI 10.1021/acs.langmuir.8b01419
ISSN 1520-5827
Citation Langmuir. 2019;35(20):65226531.

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