TY - JOUR
T1 - Size-dependent exciton substructure in CdSe nanoplatelets and its relation to photoluminescence dynamics
AU - Specht, Judith F.
AU - Scott, Riccardo
AU - Corona Castro, Marta
AU - Christodoulou, Sotirios
AU - Bertrand, Guillaume H.V.
AU - Prudnikau, Anatol V.
AU - Antanovich, Artsiom
AU - Siebbeles, Laurens D.A.
AU - Owschimikow, Nina
AU - Moreels, Iwan
AU - Artemyev, Mikhail
AU - Woggon, Ulrike
AU - Achtstein, Alexander W.
AU - Richter, Marten
PY - 2019/7/7
Y1 - 2019/7/7
N2 - CdSe nanoplatelets can be synthesized with different lateral sizes; very small nanoplatelets have almost quantum dot like features (almost discrete exciton states), while very large ones are expected to have properties of colloidal quantum wells (exciton continuum). However, nanoplatelets can be in an intermediate confinement regime with a rich substructure of excitons, which is neither quantum dot like nor an ideal 2D exciton. In this manuscript, we discuss the experimental transition energies and relaxation dynamics of exciton states in CdSe platelets with varying lateral dimensions and compare them with a microscopic theoretical model including exciton-phonon scattering. The model takes special care of the interplay of confinement and Coulomb coupling in the intermediate regime showing strong changes with respect to simple weak or strong confinement models by solving the full four dimensional lateral factorization free exciton wavefunction. Depending on the platelet size broad resonances previously attributed to just ground and excited states are actually composed of a rich substructure of several exciton states in their temporal dynamics. We show that these factorization free exciton states can explain the spectral features observed in photoluminescence experiments. Furthermore we demonstrate that the interplay of exciton bright and dark states provides principle insights into the overall temporal relaxation dynamics, and allows tuning of the exciton cooling via lateral platelet size. Our results and theoretical approach are directly relevant for understanding e.g. the size tuneability of lasing, excitonic cooling dynamics or light harvesting applications in these and similar 2D systems of finite lateral size.
AB - CdSe nanoplatelets can be synthesized with different lateral sizes; very small nanoplatelets have almost quantum dot like features (almost discrete exciton states), while very large ones are expected to have properties of colloidal quantum wells (exciton continuum). However, nanoplatelets can be in an intermediate confinement regime with a rich substructure of excitons, which is neither quantum dot like nor an ideal 2D exciton. In this manuscript, we discuss the experimental transition energies and relaxation dynamics of exciton states in CdSe platelets with varying lateral dimensions and compare them with a microscopic theoretical model including exciton-phonon scattering. The model takes special care of the interplay of confinement and Coulomb coupling in the intermediate regime showing strong changes with respect to simple weak or strong confinement models by solving the full four dimensional lateral factorization free exciton wavefunction. Depending on the platelet size broad resonances previously attributed to just ground and excited states are actually composed of a rich substructure of several exciton states in their temporal dynamics. We show that these factorization free exciton states can explain the spectral features observed in photoluminescence experiments. Furthermore we demonstrate that the interplay of exciton bright and dark states provides principle insights into the overall temporal relaxation dynamics, and allows tuning of the exciton cooling via lateral platelet size. Our results and theoretical approach are directly relevant for understanding e.g. the size tuneability of lasing, excitonic cooling dynamics or light harvesting applications in these and similar 2D systems of finite lateral size.
UR - http://www.scopus.com/inward/record.url?scp=85068235654&partnerID=8YFLogxK
U2 - 10.1039/c9nr03161h
DO - 10.1039/c9nr03161h
M3 - Article
C2 - 31204756
AN - SCOPUS:85068235654
SN - 2040-3364
VL - 11
SP - 12230
EP - 12241
JO - Nanoscale
JF - Nanoscale
IS - 25
ER -