TY - JOUR
T1 - Exciton Fine Structure and Lattice Dynamics in InP/ZnSe Core/Shell Quantum Dots
AU - Brodu, Annalisa
AU - Ballottin, Mariana V.
AU - Buhot, Jonathan
AU - Van Harten, Elleke J.
AU - Dupont, Dorian
AU - La Porta, Andrea
AU - Prins, P. Tim
AU - Tessier, Mickael D.
AU - Versteegh, Marijn
AU - Zwiller, Valery
AU - Bals, Sara
AU - Hens, Zeger
AU - Rabouw, Freddy T.
AU - Christianen, Peter C.M.
AU - De Mello Donega, Celso
AU - Vanmaekelbergh, Daniël
PY - 2018/8/15
Y1 - 2018/8/15
N2 - Nanocrystalline InP quantum dots (QDs) hold promise for heavy-metal free opto-electronic applications due to their bright and size-tunable emission in the visible range. Photochemical stability and high photoluminescence (PL) quantum yield are obtained by a diversity of epitaxial shells around the InP core. To understand and optimize the emission line shapes, the exciton fine structure of InP core/shell QD systems needs be investigated. Here, we study the exciton fine structure of InP/ZnSe core/shell QDs with core diameters ranging from 2.9 to 3.6 nm (PL peak from 2.3 to 1.95 eV at 4 K). PL decay measurements as a function of temperature in the 10 mK to 300 K range show that the lowest exciton fine structure state is a dark state, from which radiative recombination is assisted by coupling to confined acoustic phonons with energies ranging from 4 to 7 meV, depending on the core diameter. Circularly polarized fluorescence line-narrowing (FLN) spectroscopy at 4 K under high magnetic fields (up to 30 T) demonstrates that radiative recombination from the dark F = ±2 state involves acoustic and optical phonons, both from the InP core and the ZnSe shell. Our data indicate that the highest-intensity FLN peak is an acoustic phonon replica rather than a zero-phonon line, implying that the energy separation observed between the F = ±1 state and the highest-intensity peak in the FLN spectra (6 to 16 meV, depending on the InP core size) is larger than the splitting between the dark and bright fine structure exciton states.
AB - Nanocrystalline InP quantum dots (QDs) hold promise for heavy-metal free opto-electronic applications due to their bright and size-tunable emission in the visible range. Photochemical stability and high photoluminescence (PL) quantum yield are obtained by a diversity of epitaxial shells around the InP core. To understand and optimize the emission line shapes, the exciton fine structure of InP core/shell QD systems needs be investigated. Here, we study the exciton fine structure of InP/ZnSe core/shell QDs with core diameters ranging from 2.9 to 3.6 nm (PL peak from 2.3 to 1.95 eV at 4 K). PL decay measurements as a function of temperature in the 10 mK to 300 K range show that the lowest exciton fine structure state is a dark state, from which radiative recombination is assisted by coupling to confined acoustic phonons with energies ranging from 4 to 7 meV, depending on the core diameter. Circularly polarized fluorescence line-narrowing (FLN) spectroscopy at 4 K under high magnetic fields (up to 30 T) demonstrates that radiative recombination from the dark F = ±2 state involves acoustic and optical phonons, both from the InP core and the ZnSe shell. Our data indicate that the highest-intensity FLN peak is an acoustic phonon replica rather than a zero-phonon line, implying that the energy separation observed between the F = ±1 state and the highest-intensity peak in the FLN spectra (6 to 16 meV, depending on the InP core size) is larger than the splitting between the dark and bright fine structure exciton states.
KW - exciton fine structure
KW - InP/ZnSe core/shell quantum dots
KW - acoustic and optical phonons
KW - high magnetic field
UR - http://www.scopus.com/inward/record.url?scp=85050499716&partnerID=8YFLogxK
U2 - 10.1021/acsphotonics.8b00615
DO - 10.1021/acsphotonics.8b00615
M3 - Article
AN - SCOPUS:85050499716
SN - 1749-4885
VL - 5
SP - 3353
EP - 3362
JO - ACS Photonics
JF - ACS Photonics
IS - 8
ER -