Periodic Reporting for period 1 - InPlane (Colloidal two-dimensional InP nanocrystals)
Période du rapport: 2021-04-01 au 2023-03-31
Semiconductor nanocrystals (NCs) have become the most important material for colloidal nanophotonics – a rapidly advancing research field, which evolves into a powerful technological platform for lighting, biomedicine, lasing, photovoltaics, etc. This is evidenced by a steadily growing number of companies and start-ups producing and/or using NC-based materials (Nanosys, QD Vision, UbiQD, UbiGro etc.) and has led to the appearance of the consumer products – displays from Sony, TCL, and Samsung. By some estimates, such displays have higher luminance and are 25 % more efficient than organic LEDs, and by 2025 60 % of TVs and 50 % of monitors may include NC-based materials. However, most of the success was achieved with the NCs composed of cadmium chalcogenides, which became a severe obstacle with the tightening of restrictions on the use of toxic materials in consumer products. This highlighted the need and stimulated the research and development of new materials meeting the criteria of environmental regulations as well as satisfying the requirements of the industry.
Among the alternatives, NCs comprised of III-V semiconductors stand out not only due to their relatively benign nature but also due to expected higher robustness because of the high covalency of the crystalline structure, a broad range of bandgaps spanning from ultraviolet to deep-infrared regions, efficient light absorption, and high mobility of charge carriers. Although the first syntheses of such NCs were reported at around the same time as II-VI and IV-VI ones, the state-of-the-art III-V nanomaterials are still noticeably inferior to their Cd- and Pb-chalcogenide-based counterparts. To tackle this issue, several problems need to be addressed, including broadening the range of synthetic precursors, designing new synthetic strategies, elucidation of NC formation mechanisms, and investigation of surface chemistry of NCs for controlling their shape, electronic and optical properties as well as tailoring III-V nanoparticles for applications.
The main objective of this Marie Skłodowska-Curie action is the implementation of an innovative approach to address several of these points by focusing on the design of synthetic procedures and the investigation of the new type of NCs – colloidal two-dimensional indium phosphide NCs – that may become new nontoxic material for LEDs and displays with superior efficiency, optical characteristics, and simple device structure.
Among the alternatives, NCs comprised of III-V semiconductors stand out not only due to their relatively benign nature but also due to expected higher robustness because of the high covalency of the crystalline structure, a broad range of bandgaps spanning from ultraviolet to deep-infrared regions, efficient light absorption, and high mobility of charge carriers. Although the first syntheses of such NCs were reported at around the same time as II-VI and IV-VI ones, the state-of-the-art III-V nanomaterials are still noticeably inferior to their Cd- and Pb-chalcogenide-based counterparts. To tackle this issue, several problems need to be addressed, including broadening the range of synthetic precursors, designing new synthetic strategies, elucidation of NC formation mechanisms, and investigation of surface chemistry of NCs for controlling their shape, electronic and optical properties as well as tailoring III-V nanoparticles for applications.
The main objective of this Marie Skłodowska-Curie action is the implementation of an innovative approach to address several of these points by focusing on the design of synthetic procedures and the investigation of the new type of NCs – colloidal two-dimensional indium phosphide NCs – that may become new nontoxic material for LEDs and displays with superior efficiency, optical characteristics, and simple device structure.
The project implementation comprised three scientific work packages plus communication and dissemination activities.
In the first work package, we investigated approaches for the “direct” synthesis of indium phosphide nanoplatelets. First, we synthesized new phosphorus-containing precursors for the synthesis of indium phosphide nanocrystals and explored their performance in synthesis. Then we focused on exploring approaches for the preparation of indium phosphide nanoplatelets through the recrystallization of small indium phosphide nanocrystals and magic-size clusters in the presence of shape control agents.
In the second work package, we investigated the “indirect” synthesis route to indium phosphide nanoplatelets by performing In3+-for-Cu+ cation exchange in copper phosphide nanotemplates. This route exploits the difference in binding affinities of phosphines to Cu+ and In3+ ions, the high mobility of Cu+ ions in the lattice as well as the tendency of copper phosphide nanocrystals for two-dimensional growth directed by its crystalline lattice.
Finally, the third work package was focused on the modification of indium phosphide nanocrystals (mainly by the preparation of core-shell heterostructures) to meet the needs of practical applications as well as comprehensively study their optoelectronic properties to make them bright, efficient, and stable material for light-emitting devices.
The results and activities of the project were disseminated through peer-reviewed publications, participation in conferences and workshops. As of the end date of the project, it yielded one peer-reviewed paper with three more in preparation (not including three planned co-authored papers, three oral talks, and three poster presentations at specialized conferences. To provide public engagement, communicate the results of the action and broad general information about nanomaterials the fellow also took part in Dresden Long Night of Science, UNI-TAG – TU Dresden’s open house day for prospective students and provided an entry to 2023 cfaed Scientific Image Competition, which can be used in promotional materials in public outreach activities of TU Dresden and cfaed.
In the first work package, we investigated approaches for the “direct” synthesis of indium phosphide nanoplatelets. First, we synthesized new phosphorus-containing precursors for the synthesis of indium phosphide nanocrystals and explored their performance in synthesis. Then we focused on exploring approaches for the preparation of indium phosphide nanoplatelets through the recrystallization of small indium phosphide nanocrystals and magic-size clusters in the presence of shape control agents.
In the second work package, we investigated the “indirect” synthesis route to indium phosphide nanoplatelets by performing In3+-for-Cu+ cation exchange in copper phosphide nanotemplates. This route exploits the difference in binding affinities of phosphines to Cu+ and In3+ ions, the high mobility of Cu+ ions in the lattice as well as the tendency of copper phosphide nanocrystals for two-dimensional growth directed by its crystalline lattice.
Finally, the third work package was focused on the modification of indium phosphide nanocrystals (mainly by the preparation of core-shell heterostructures) to meet the needs of practical applications as well as comprehensively study their optoelectronic properties to make them bright, efficient, and stable material for light-emitting devices.
The results and activities of the project were disseminated through peer-reviewed publications, participation in conferences and workshops. As of the end date of the project, it yielded one peer-reviewed paper with three more in preparation (not including three planned co-authored papers, three oral talks, and three poster presentations at specialized conferences. To provide public engagement, communicate the results of the action and broad general information about nanomaterials the fellow also took part in Dresden Long Night of Science, UNI-TAG – TU Dresden’s open house day for prospective students and provided an entry to 2023 cfaed Scientific Image Competition, which can be used in promotional materials in public outreach activities of TU Dresden and cfaed.
Although the main objective of the action (development of the procedures for the synthesis of brightly emitting InP NPls) was not achieved, the results of the project significantly contributed to the synthetic chemistry of III-V semiconductor NCs by the introduction of new types of phosphorus and arsenic precursors, the number of which is at the moment significantly restricted. The advantage of the introduced pnictogen sources is their relatively simple and low-cost synthesis with the ability to modify their reactivity by tuning the nature of side alkyl chains. In addition, unlike existing phosphorus and arsenic precursors, some of the newly introduced ones are non-volatile, non-pyrophoric, and somewhat air-stable, which is extremely important for the large-scale synthesis of III-V nanomaterials in the industrial setting. Moreover, they can be used as starting materials for the preparation of precursors specifically tailored for particular synthetic requirements.