title: Supercrystals of CdSe quantum dots with high charge mobility and efficient electron transfer to TiO2.
abstract: Thermal annealing of thin films of CdSe/CdS core/shell quantum dots induces superordering of the nanocrystals and a significant reduction of the interparticle spacing. This results in a drastic enhancement of the quantum yield for charge carrier photogeneration and the charge carrier mobility. The mobile electrons have a mobility as high as 0.1 cm(2)/(V x s), which represents an increase of 4 orders of magnitude over non-annealed QD films and exceeds existing literature data on the electron mobility in CdSe quantum dot films. The lifetime of mobile electrons is longer than that of the exciton. A fraction of the mobile electrons gets trapped at levels below the conduction band of the CdSe nanocrystals. These electrons slowly diffuse over 50-300 nm on longer times up to 20 micros and undergo transfer to a TiO2 substrate. The yield for electron injection in TiO2 from both mobile and trapped electrons is found to be >16%.
authors.affiliation: Optoelectronic Materials Section, Department of Chemical Engineering, Delft University of Technology, Julianalaan 136, 2628 BL Delft, The Netherlands.
authors.forename: Elise
authors.initials: E
authors.lastname: Talgorn
authors.forename: Ruben D
authors.initials: RD
authors.lastname: Abellon
authors.forename: Patricia J
authors.initials: PJ
authors.lastname: Kooyman
authors.forename: Jorge
authors.initials: J
authors.lastname: Piris
authors.forename: Tom J
authors.initials: TJ
authors.lastname: Savenije
authors.forename: Albert
authors.initials: A
authors.lastname: Goossens
authors.forename: Arjan J
authors.initials: AJ
authors.lastname: Houtepen
authors.forename: Laurens D A
authors.initials: LD
authors.lastname: Siebbeles