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Posted: May 15, 2017
The ultimate tuning of optoelectric properties with nanoplatelets
(Nanowerk News) An international research team has demonstrated an easy approach to synthesize ultrasmall near infrared 2D nanoplatelets (NIR NPLs) via template-assisted cation exchange.
The NPLs (PbSe or alloyed PbSe1–xSx) with lateral dimensions below 10 nm exhibit continuously tunable photoluminescence emission ranging from 1180 to 1380 nm thanks to the variation of the S/Se ratio, which cannot be achieved in binary NPLs, and a quantum yield of ∼60%, the highest reported for NIR NPLs so far.
NPLs exhibit a series of outstanding optoelectronic properties for various applications in energy technologies, such as solar cells or solar-driven hydrogen production, because of their suitable electronic band structure for fast exciton dissociation, efficient charge transfer of photogenerated electron/hole pairs, and high photochemical stability.
Near infrared NPLs based on lead or tin chalcogenides enable a thickness-tunable wide absorption spectrum, ranging from ultraviolet to NIR, thereby matching the solar spectrum with significant overlap.
The authors write that theoretical simulations of the bandgap as a function of thickness, geometry, and size show that ultrasmall NPLs exhibit strong 3D quantum confinement, compared to 1D confinement in larger sized NPLs with similar thickness.
As a proof-of-concept, the team used the NPLs as photosensitizers for PEC hydrogen generation. After surface treatment with Cd, they obtained a saturated photocurrent density of ∼5 mA cm-2, nearly three times higher than the value obtained from PbS/CdS QDs under identical preparation and measurement conditions.