Asaduzzaman Abu, Runge Keith, Deymier Pierre, Muralidharan Krishna
School of Science, Engineering and Technology, Pennsylvania State University - Harrisburg, Middletown, Pennsylvania 17057, United States.
Materials Science and Engineering, University of Arizona, Tucson, Arizona 85721, United States.
Langmuir. 2020 Nov 10;36(44):13312-13319. doi: 10.1021/acs.langmuir.0c02425. Epub 2020 Oct 28.
A first-principles density functional theory calculation was carried out to study the adsorption of acetic acid, methyl amine, methanethiol, and hydrogen iodide on the (100) surface of PbS. All four ligands are common capping agents used in colloidal PbS quantum dot-based photovoltaics. Interestingly, among the considered adsorbates, dissociative adsorption was energetically preferred for hydrogen iodide, while associative adsorption was favorable for the rest. Associative adsorption was driven by strong interactions between the electronegative elements (Y) in the respective ligands and the Pb surface atoms via Pb 6-Y bond hybridization ( represents the valence quantum number of the respective electronegative elements). Importantly, the adsorption of ligands altered the work function of PbS, with contrasting trends for associative (decrease in the work function) versus dissociative (increase in the work function) adsorption. The changes in the work function correlates well with a corresponding shift in the 5d level of surface Pb atoms. Other important observations include variations in the work function that linearly change with increasing the surface coverage of adsorbed ligands as well as with the strength of the adsorption of ligands.
