Doping-induced photoluminescence tuning of lead-free metal halide perovskite nanocrystals
Schanz, Max (2021)
2021
Master's Programme in Materials Science and Engineering
Tekniikan ja luonnontieteiden tiedekunta - Faculty of Engineering and Natural Sciences
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Hyväksymispäivämäärä
2021-12-09
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:tuni-202111288731
https://urn.fi/URN:NBN:fi:tuni-202111288731
Tiivistelmä
Metal halide perovskite nanocrystals have been extensively studied in recent years. Their beneficial features are, among others, remarkable optical and excitonic properties and their tunable bandgap. Furthermore, their easy and low-cost colloidal synthesis is a big advantage over competing semiconductor nanocrystals. However, many metal halide perovskite materials rely on toxic elements, such as lead, or suffer from stability issues in ambient conditions. This work aims to contribute to the search for a lead-free alternative for photoluminescent applications.
The approach followed in this work was to start from the known non-luminescent, high band gap 0D perovskite derivative Rb3InCl6 and eventually induce and tune photoluminescence by doping with different elements, such as Sb, Mn, and Bi.
The nanocrystals were synthesized via the hot injection technique, a colloidal method based on the swift injection of one precursor solution into another at an elevated temperature to induce fast nucleation and crystallization. After the synthesis and multistage purification, the Rb3InCl6 nanocrystal suspensions have then been characterized by various methods, such as X-ray diffraction, UV-Vis absorption spectroscopy, fluorescence spectroscopy, inductively coupled plasma mass spectrometry and transmission electron microscopy.
For all doping experiments, nanocrystals with different concentrations of the respective dopants were tested. In the first sample series, doping with Sb3+ did not yield the anticipated outcome, as the reported photoluminescence could not be reproduced. The next dopant, Mn2+ showed a minor feature in the photoluminescence at ∼640 nm. However, the absorption of this material is not high enough to enable a reasonable emission. Doping with Bi3+ ions induced a bright blue luminescence (∼400 nm), because the additional Bi-related energy states give rise to a sharp absorption peak at 330 nm. Finally, co-doping with Bi3+ and Mn2+ ions also enabled the energy transfer to the Mn states and increased the related red emission to a considerable intensity. This allowed for gradual color tuning from blue, over violet and pink to red, depending on the dopant concentrations.
This work is the first to report a systematic approach for photoluminescent color tuning in Rb3InCl6 nanocrystals. Furthermore, the conclusions drawn from the conducted doping series lead to a better understanding of the underlying physical processes related to doping-induced photoluminescence in non-luminescent nanocrystals, as well as color tuning.
The approach followed in this work was to start from the known non-luminescent, high band gap 0D perovskite derivative Rb3InCl6 and eventually induce and tune photoluminescence by doping with different elements, such as Sb, Mn, and Bi.
The nanocrystals were synthesized via the hot injection technique, a colloidal method based on the swift injection of one precursor solution into another at an elevated temperature to induce fast nucleation and crystallization. After the synthesis and multistage purification, the Rb3InCl6 nanocrystal suspensions have then been characterized by various methods, such as X-ray diffraction, UV-Vis absorption spectroscopy, fluorescence spectroscopy, inductively coupled plasma mass spectrometry and transmission electron microscopy.
For all doping experiments, nanocrystals with different concentrations of the respective dopants were tested. In the first sample series, doping with Sb3+ did not yield the anticipated outcome, as the reported photoluminescence could not be reproduced. The next dopant, Mn2+ showed a minor feature in the photoluminescence at ∼640 nm. However, the absorption of this material is not high enough to enable a reasonable emission. Doping with Bi3+ ions induced a bright blue luminescence (∼400 nm), because the additional Bi-related energy states give rise to a sharp absorption peak at 330 nm. Finally, co-doping with Bi3+ and Mn2+ ions also enabled the energy transfer to the Mn states and increased the related red emission to a considerable intensity. This allowed for gradual color tuning from blue, over violet and pink to red, depending on the dopant concentrations.
This work is the first to report a systematic approach for photoluminescent color tuning in Rb3InCl6 nanocrystals. Furthermore, the conclusions drawn from the conducted doping series lead to a better understanding of the underlying physical processes related to doping-induced photoluminescence in non-luminescent nanocrystals, as well as color tuning.