title: Photoluminescence from quasi-type-II spherical CdSe-CdS core-shell quantum dots.
abstract: Spherical CdSe-CdS core-shell quantum dots (QDs) are found to be flexible in the transition between the type-I regime and the type-II regime with different core/shell dimensions. The quasi-type-II feature of the colloidal dots is confirmed with time-resolved photoluminescence (PL) measurements. Two recombination paths of the excitons with significantly different decay rates are observed and analyzed. The spherical CdSe-CdS core-shell QDs are numerically simulated to investigate the carrier separation. A relatively long radiative lifetime and high degree of spatial carrier separation provide good potential to achieve lasing under continuous-wave excitation. Amplified spontaneous emission at room temperature is detected from the QDs embedded in the polymer matrix. It is shown that a larger shell thickness results in a lower pumping threshold, while a smaller shell thickness leads to higher PL efficiency.
authors.affiliation: Royal Institute of Technology, Division of Optics, Kista SE-164 40, Sweden. lindong@kth.se
authors.forename: Lin
authors.initials: L
authors.lastname: Dong
authors.forename: Abhilash
authors.initials: A
authors.lastname: Sugunan
authors.forename: Jun
authors.initials: J
authors.lastname: Hu
authors.forename: Sicheng
authors.initials: S
authors.lastname: Zhou
authors.forename: Shanghua
authors.initials: S
authors.lastname: Li
authors.forename: Sergei
authors.initials: S
authors.lastname: Popov
authors.forename: Muhammet S
authors.initials: MS
authors.lastname: Toprak
authors.forename: Ari T
authors.initials: AT
authors.lastname: Friberg
authors.forename: Mamoun
authors.initials: M
authors.lastname: Muhammed