Probing Excitons in Ultrathin PbS Nanoplatelets with Enhanced Near-Infrared Emission
arXiv:2011.07174 · doi:10.1021/acs.jpclett.0c03461
Abstract
Strongly quantum-confined 2D colloidal PbS nanoplatelets (NPLs) are highly interesting materials for near-infrared optoelectronic applications. Here, we use ultrafast transient optical absorption spectroscopy to study the characteristics and dynamics of photoexcited excitons in ultrathin PbS NPLs with a cubic (rock-salt) structure. The NPLs are synthesized at near room temperature from lead oleate and thiourea precursors and show an optical absorption onset at 680 nm (1.8 eV) as well as photoluminescence at 720 nm (1.7 eV). By treating PbS NPLs with CdCl2 in a post-synthetic step, their photoluminescence quantum yield is strongly enhanced from 1.4 % to 19.4 %. The surface treatment leads to an increased lead to sulfur ratio in the structures and associated reduced non-radiative recombination. Exciton-phonon interactions in pristine and CdCl2 treated PbS NPLs at frequencies of 1.8 and 2.2 THz are apparent from coherent oscillations in the measured transient absorption spectra. This study is an important step forward in unraveling and controlling the optical properties of IV-VI semiconductor NPLs.
References in corpus (7)
- Ultra-thin PbS sheets by two-dimensional oriented attachment
- How semiconductor nanoplatelets form
- Influence of the Surface of a Nanocrystal on its Electronic and Phononic Properties
- Tailoring the height of ultrathin PbS nanosheets and their application as field-effect transistors
- From dots to stripes to sheets - Shape control of lead sulfide nanostructures
- Photoexcitation of PbS Nanosheets Leads to Highly Mobile Charge Carriers and Stable Excitons
- Effects of electron-phonon interactions on the electron tunneling spectrum of PbS quantum dots