title: Light-induced charged and trap states in colloidal nanocrystals detected by variable pulse rate photoluminescence spectroscopy.
abstract: Intensity instabilities are a common trademark of the photoluminescence of nanoemitters. This general behavior is commonly attributed to random fluctuations of free charges and activation of charge traps reducing the emission yield intermittently. However, the actual physical origin of this phenomenon is actively debated. Here we devise an experiment, variable pulse rate photoluminescence, to control the accumulation of charges and the activation of charge traps. The dynamics of these states is studied, with pulse repetition frequencies from the single-pulse to the megahertz regime, by monitoring photoluminescence spectrograms with picosecond temporal resolution. We find that both photocharging and charge trapping contribute to photoluminescence quenching, and both processes can be reversibly induced by light. Our spectroscopic technique demonstrates that charge accumulation and trap formation are strongly sensitive to the environment, showing different dynamics when nanocrystals are dispersed in solution or deposited as a film.
authors.affiliation: Dipartimento di Fisica, Università di Cagliari, I-09042 Monserrato, Italy. saba@unica.it
authors.forename: Michele
authors.initials: M
authors.lastname: Saba
authors.forename: Mauro
authors.initials: M
authors.lastname: Aresti
authors.forename: Francesco
authors.initials: F
authors.lastname: Quochi
authors.forename: Marco
authors.initials: M
authors.lastname: Marceddu
authors.forename: Maria Antonietta
authors.initials: MA
authors.lastname: Loi
authors.forename: Jing
authors.initials: J
authors.lastname: Huang
authors.forename: Dmitri V
authors.initials: DV
authors.lastname: Talapin
authors.forename: Andrea
authors.initials: A
authors.lastname: Mura
authors.forename: Giovanni
authors.initials: G
authors.lastname: Bongiovanni
mesh_terms: D003102:Colloids / Q000737:chemistry* / Q000528:radiation effects; D003460:Crystallization / Q000379:methods; D008027:Light; D008163:Luminescent Measurements / Q000379:methods*; D008422:Materials Testing; D049329:Nanostructures / Q000737:chemistry* / Q000528:radiation effects / Q000648:ultrastructure*; D010316:Particle Size; D055672:Static Electricity
chemical_list: D003102:Colloids