Photoexcitation of PbS Nanosheets Leads to Highly Mobile Charge Carriers and Stable Excitons

Abstract

Solution-processable two-dimensional (2D) semiconductors with chemically tunable thickness and associated tunable band gaps are highly promising materials for ultrathin optoelectronics. Here, the properties of free charge carriers and excitons in 2D PbS nanosheets of different thickness are investigated by means of optical pump-terahertz probe spectroscopy. By analyzing the frequency-dependent THz response, a large quantum yield of excitons is found. The scattering time of free charge carriers increases with nanosheet thickness, which is ascribed to reduced effects of surface defects and ligands in thicker nanosheets. The data discussed provide values for the DC mobility in the range 550 - 1000 cm2/Vs for PbS nanosheets with thicknesses ranging from 4 to 16 nm. Results underpin the suitability of colloidal 2D PbS nanosheets for optoelectronic applications.

References in corpus (9)

• Ultra-thin PbS sheets by two-dimensional oriented attachment
• Low-threshold stimulated emission using colloidal quantum wells
• Field-effect transistors made of individual colloidal PbS nanosheets
• Tailoring the height of ultrathin PbS nanosheets and their application as field-effect transistors
• Towards colloidal spintronics through Rashba spin-orbit interaction in lead sulphide nanosheets
• Photovoltaic effect in individual asymmetrically contacted lead sulfide nanosheets
• Transient terahertz spectroscopy of excitons and unbound carriers in quasi two-dimensional electron-hole gases
• High Performance n- and p-Type Field-Effect Transistors Based on Hybridly Surface-Passivated Colloidal PbS Nanosheets
• New ways to synthesize lead sulfide nanosheets - substituted alkanes direct the growth of 2D nanostructures

Cited by in corpus (4)

• Probing Excitons in Ultrathin PbS Nanoplatelets with Enhanced Near-Infrared Emission
• Colloidal two-dimensional metal chalcogenides: Realization and application of the structural anisotropy
• Biexcitons in Highly Excited CdSe Nanoplatelets
• Solving the Synthetic Riddle of Colloidal 2D PbTe Nanoplatelets with Tunable Near-Infrared Emission