Proceedings of nanoGe Spring Meeting 2022 (NSM22)
DOI: https://doi.org/10.29363/nanoge.nsm.2022.388
Publication date: 7th February 2022
2D lead chalcogenide nanoplatelets and nanosheets are highly topical materials for near-infrared (NIR) optoelectronic applications, providing solutions with bandgaps tailored to the spectral windows necessary for biological imaging and glass fiber optics.[1] While extensive work has been published on lead chalcogenide nanocrystals and thicker nanosheets, atomically thin nanoplatelets only recently moved into focus.[2],[3],[4] Lead chalcogenide nanoplatelets combine the inherent advantages of 2D materials, such as monodispersity in thickness and increased exciton binding energies, with a large exciton-Bohr radius and multiple exciton generation.[5]
In this work, we present 2D PbSe NPLs with cubic rock salt crystal structure synthesized at low reaction temperatures of 0 °C and room temperature. The optoelectronic properties have been analysed using steady state and ultrafast transient optical spectroscopy. A lateral size tuning of the PbSe NPLs by controlling the temperature and by adding small amounts of octylamine to the reaction leads to excitonic absorption features in the range of 800 – 1000 nm (1.6 – 1.3 eV) and narrow photoluminescence (PL) seamlessly covering the broadband infrared spectral window of 900 – 1450 nm (1.4 – 0.9 eV). The PL quantum yield of the as-synthesized PbSe NPLs is more than doubled by a postsynthetic treatment with CdCl2 (e.g. from 14.7 % to 37.4 % for NPLs emitting at 980 nm). The origin of this increase being trap-state emission and how the treatment reduces its contribution is revealed by photoluminescence (PL) shape analysis, PL lifetime measurements and transient absorption measurements. Our results open up new pathways for a direct synthesis and straightforward incorporation of colloidal PbSe NPLs as efficient infrared emitters at technologically relevant telecommunication wavelength.
The project leading to these results was funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany’s Excellence Strategy within the Cluster of Excellence PhoenixD (EXC 2122, Project ID 390833453). The authors thank the Laboratory for Nano and Quantum Engineering (LNQE) in Hannover for access to the TEM. We thank Prof. Nadja-C. Bigall for access to the photoluminescence spectrometer and Prof. Dirk Dorfs for access to the UV-Vis-NIR absorption spectrometer.
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