Digital picture of colloidal solution in toluene taken under UV-light (λ = 365 nm) and crystal structure of Formamidinium lead-halide perovskite. (Image: Friedrich-Alexander-Universität Erlangen-Nürnberg)
The team reports facile and rapid room temperature synthesis of cubic and platelet-like colloidal nanocrystals (NCs) of Formamidinium Lead Halide Perovskite FAPbX3 (X=Cl, Br, I, or mixed Cl/Br and Br/I) by ligand-assisted re-precipitation method (LARP).
The obtained NCs are 15-25 nm in size and exhibit a remarkably high photoluminescence quantum yield of up to 85% as well as colloidal and chemical stability.
The cubic and platelet-like NCs with their emission in the range of 415-740 nm, full width at half maximum of 20-44 nm and radiative lifetimes of 5-166 ns, allow precise band gap tuning by halide composition as well as by tailoring their dimensions.
Notably, for the first time they have demonstrate thermodynamically stable FAPbI3 NCs in the black cubic α-phase without transition to the yellow hexagonal δ-phase even after 150 days of storage. This is in strong contrast to polycrystalline films and single crystals which convert within hours.
This fact paves the way to highly efficient perovskite based quantum dots photovoltaics, which is underpinned by demonstrating FAPbI3 NCs based photodetector.
To highlight the potential of FAPbX3 NCs as a promising candidate for optoelectronic and luminescent applications, the scientists modified the surface with polyhedral oligomeric silsesquioxane. This modification protects the brightly luminescent FAPbX3 NCs from decomposition even after storage in water for more than 2 months.