Proceedings of nanoGe Fall Meeting 2021 (NFM21)
DOI: https://doi.org/10.29363/nanoge.nfm.2021.020
Publication date: 23rd September 2021
Quantum dots (QDs) are novel, nano-sized semiconductors with a size-tunable bandgap due to the quantum confinement effect [1]. Over the past few decades, the surface passivation of Cd- and Pb-based QDs has been studied using both experimental and computational methods, leading to significant advancements in the preparation of high-quality Cd- and Pb-based QDs [2,3]. Unfortunately, the toxicity of Cd- and Pb-based QDs often limits the utility of these QDs in consumer devices [4]. In recent years, indium phosphide (InP) has rapidly gained attention as a non-toxic alternative to Cd-based QDs [5]. However, as-synthesized InP QDs have a large density of trap states originating from unsaturated surface atoms, resulting in low PLQYs [5,6].
We report post-synthetic surface passivation utilizing benzoic acid (BZA) as an X-type surface ligand. To understand how BZA impacts their electronic structure, we conducted spectroscopic studies on InP QDs with various surface modifications, including in-situ fluorination and post-synthetic BZA treatment. Comparison of a variety of time-resolved spectroscopic techniques reveals that BZA can selectively remove electron trap states in InP QDs by passivating unsaturated indium atoms at the QD surface. When the BZA treatment is used in combination with a well-established fluoride treatment, the photoluminescence quantum yield of these unshelled InP QDs exceeds 20%. Compared with previous post-synthetic methods to increase the performance of InP QDs, including treatment with Z-type ligands and HF etching, the BZA treatment is green, safe, and easy to use. This research advances our understanding of the function of X-type ligands as passivants for unsaturated indium atoms for the post-synthetic treatment of InP QDs.
This work was supported by the Organic Materials Chemistry Program in the Air Force Office of Scientific Research (FA9550-18-1-0331). This work was performed in part at the Analytical Instrumentation Facility (AIF) at North Carolina State University, which is supported by the State of North Carolina and the National Science Foundation (award number ECCS-1542015). This work made use of instrumentation at AIF acquired with support from the National Science Foundation (DMR-1726294). The AIF is a member of the North Carolina Research Triangle Nanotechnology Network (RTNN), a site in the National Nanotechnology Coordinated Infrastructure (NNCI).
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