Periodic Reporting for period 4 - PINNACLE (Perovskite Nanocrystal-Nanoreactors for Enhanced Light Emission)
Reporting period: 2022-09-01 to 2023-08-31
Halide perovskites have emerged as a material to enhance and possibly replace conventional semiconductor materials for optoelectronics. Solar conversion efficiencies already rival those of silicon, and EQE values for perovskite-based LEDs have surpassed the 20% mark for the green and infrared part of the optical spectrum. However, several issues still prevent the widespread commercialization of halide perovskites. The most prominent of these issues is their susceptibility to environmentally-induced degradation, a propensity of the ions to migrate through the crystal structure, and diminished efficiency in the blue part of the spectrum. To be able to mitigate these problems, one must first understand in detail the morphology and the interplay with electronic, optical, and phononic properties.
PINNACLE aims to develop novel micellar-encapsulated perovskite NCs, which will prevent environmentally-induced degradation and (halide) ion migration. This will lead to increased stabilities and enable the realization of otherwise inaccessible (nano-)structures. Furthermore, the controllable synthesis and positioning of single crystals will allow for a detailed study of the fundamental properties of these NCs and an insight into how to manipulate the strategically.
The insights gained and optimized NCs will be incorporated into working devices to demonstrate the principles learned and provide a feedback loop for optimizing the synthesis.
PINNACLE aims to develop novel micellar-encapsulated perovskite NCs, which will prevent environmentally-induced degradation and (halide) ion migration. This will lead to increased stabilities and enable the realization of otherwise inaccessible (nano-)structures. Furthermore, the controllable synthesis and positioning of single crystals will allow for a detailed study of the fundamental properties of these NCs and an insight into how to manipulate the strategically.
The insights gained and optimized NCs will be incorporated into working devices to demonstrate the principles learned and provide a feedback loop for optimizing the synthesis.
PINNACLE is a highly interdisciplinary research project encompassing elements from physics, chemistry, material science, and engineering. Accordingly, a diverse team of young, highly motivated researchers with expertise ranging from inorganic chemistry to spectroscopy, theoretical physics, and device engineering worked together to fulfil the project's goals of enhancing the understanding of halide perovskite nanocrystals and using this knowledge to push them further towards commercialization. Due to the Corona pandemic, the overall goals had to be shifted away from the device application and more toward the fundamental understanding of perovskites and mitigation of the material’s current limitations.
Toward the fundamental understanding, we extensively investigated strongly confined halide perovskite NCs, focusing mainly on hitherto less explored anisotropic NCs such as nanorods and nanoplatelets. Incorporating machine learning and various characterization methods (X-ray scattering, electron microscopy, in situ optical spectroscopy) we have been able to develop reproducible, highly efficient syntheses working in ambient conditions for the specific fabrication of thickness-controlled 1D and 2D nanocrystals. These provide an excellent basis for studying the intricate interplay between morphology, composition and resulting properties of halide perovskites. We have probed these with complex temperature-resolved ultrafast optical spectroscopy, revealing important details on, e.g. excitonic fine structure, phonon-coupling exciton-exciton annihilation. The micellar-encapsulated NCs have also been significantly enhanced and now con be produced with strong emission spanning the visible wavelength and superior stability toward environmental degradation. Post-processing cross-linking leads to extremely stable films and heterostructures. With the resources and research environment provided through PINNACLE, we have now shifted our focus toward lead-free perovskite alternatives and exploring materials for photocatalysis.
This work so far has culminated in a number of invited and contributed talks for the PINNACLE team, with several awards for students’ presentations, and many high-impact papers. We have submitted two patents and are contemplating a proof-of-concept grant application to explore the commercial viability of our approaches.
Toward the fundamental understanding, we extensively investigated strongly confined halide perovskite NCs, focusing mainly on hitherto less explored anisotropic NCs such as nanorods and nanoplatelets. Incorporating machine learning and various characterization methods (X-ray scattering, electron microscopy, in situ optical spectroscopy) we have been able to develop reproducible, highly efficient syntheses working in ambient conditions for the specific fabrication of thickness-controlled 1D and 2D nanocrystals. These provide an excellent basis for studying the intricate interplay between morphology, composition and resulting properties of halide perovskites. We have probed these with complex temperature-resolved ultrafast optical spectroscopy, revealing important details on, e.g. excitonic fine structure, phonon-coupling exciton-exciton annihilation. The micellar-encapsulated NCs have also been significantly enhanced and now con be produced with strong emission spanning the visible wavelength and superior stability toward environmental degradation. Post-processing cross-linking leads to extremely stable films and heterostructures. With the resources and research environment provided through PINNACLE, we have now shifted our focus toward lead-free perovskite alternatives and exploring materials for photocatalysis.
This work so far has culminated in a number of invited and contributed talks for the PINNACLE team, with several awards for students’ presentations, and many high-impact papers. We have submitted two patents and are contemplating a proof-of-concept grant application to explore the commercial viability of our approaches.
The encapsulated perovskite NCs devised within the PINNACLE project already have stability far surpassing conventional perovskite NCs. Emission efficiencies are already comparable to standard NCs in parts of the optical spectrum, and we hope to extend this to the entire visible range. As the materials required are highly abundant and cost-effective, we envision halide perovskites becoming a material of choice for commercially viable LEDs and even lasers.