title: Time-Resolved Stark Spectroscopy in CdSe Nanoplatelets: Exciton Binding Energy, Polarizability, and Field-Dependent Radiative Rates.
abstract: We present a study of the application potential of CdSe nanoplatelets (NPLs), a model system for colloidal 2D materials, as field-controlled emitters. We demonstrate that their emission can be changed by 28% upon application of electrical fields up to 175 kV/cm, a very high modulation depth for field-controlled nanoemitters. From our experimental results we estimate the exciton binding energy in 5.5 monolayer CdSe nanoplatelets to be EB= 170 meV; hence CdSe NPLs exhibit highly robust excitons which are stable even at room temperature. This opens up the possibility to tune the emission and recombination dynamics efficiently by external fields. Our analysis further allows a quantitative discrimination of spectral changes of the emission energy and changes in PL intensity related to broadening of the emission line width as well as changes in the intrinsic radiative rates which are directly connected to the measured changes in the PL decay dynamics. With the developed field-dependent population model treating all occurring field-dependent effects in a global analysis, we are able to quantify, e.g., the ground state exciton transition dipole moment (3.0 × 10-29Cm) and its polarizability, which determine the radiative rate, as well as the (static) exciton polarizability (8.6 × 10-8eV cm2/kV2), all in good agreement with theory. Our results show that an efficient field control over the exciton recombination dynamics, emission line width, and emission energy in these nanoparticles is feasible and opens up application potential as field-controlled emitters.
authors.affiliation: Institute of Optics and Atomic Physics, Technical University of Berlin , Strasse des 17. Juni 135, 10623 Berlin, Germany.
authors.forename: Riccardo
authors.initials: R
authors.lastname: Scott
authors.affiliation: Institute of Optics and Atomic Physics, Technical University of Berlin , Strasse des 17. Juni 135, 10623 Berlin, Germany.|Optoelectronic Materials Section, Delft University of Technology , 2628 BL Delft, The Netherlands.
authors.forename: Alexander W
authors.initials: AW
authors.lastname: Achtstein
authors.affiliation: Research Institute for Physical Chemical Problems of Belarusian State University , 220006, Minsk, Belarus.
authors.forename: Anatol V
authors.initials: AV
authors.lastname: Prudnikau
authors.affiliation: Research Institute for Physical Chemical Problems of Belarusian State University , 220006, Minsk, Belarus.
authors.forename: Artsiom
authors.initials: A
authors.lastname: Antanovich
authors.affiliation: Optoelectronic Materials Section, Delft University of Technology , 2628 BL Delft, The Netherlands.
authors.forename: Laurens D A
authors.initials: LD
authors.lastname: Siebbeles
authors.affiliation: Research Institute for Physical Chemical Problems of Belarusian State University , 220006, Minsk, Belarus.
authors.forename: Mikhail
authors.initials: M
authors.lastname: Artemyev
authors.affiliation: Institute of Optics and Atomic Physics, Technical University of Berlin , Strasse des 17. Juni 135, 10623 Berlin, Germany.
authors.forename: Ulrike
authors.initials: U
authors.lastname: Woggon
keywords: Field-dependent PL; Franz-Keldysh effect; exciton binding energy; nanoplatelets; quantum confined Stark effect