Electrochemical Evaluation of Dopant Energetics and the Modulation of Ultrafast Carrier Dynamics in Cu-Doped CdSe Nanocrystals

• Published in: Journal of physical chemistry. C Vol. 121; no. 48; pp. 27233 - 27240
• Main Authors: Maiti, Sourav, Dana, Jayanta, Jadhav, Yogesh, Debnath, Tushar, Haram, Santosh K, Ghosh, Hirendra N
• Format: Journal Article
• Language: English
• Published: American Chemical Society 07-12-2017
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/acs.jpcc.7b10262

Cyclic voltammetric and femtosecond transient absorption (TA) measurements on Cu+-doped CdSe nanocrystals (NCs) were utilized to reveal the energetics of the electroactive Cu+ dopant with respect to the band energies of CdSe NC host and the influence of Cu in tuning the carrier dynamics, respectively. Oxidation–reduction peaks due to an electroactive dopant within CdSe NC host have been traced to determine its energy level which was correlated to the dopant emission energy and Stokes shift. The low doping density of Cu does not significantly alter the band structure of CdSe as the shape of the TA spectra remains similar before and after doping. However, Cu+ acts as a hole localizing center decoupling the electronic wave function from the hole leading to slower Auger-assisted electron cooling in doped NCs. As hole localization to Cu+ is the primary step for dopant emission, in the presence of hole quenchers (aminophenols) the dopant emission gets drastically quenched. Interestingly, once hole is captured by Cu+ due to strong affinity for electron, external quenchers (nitrophenols) are unable to capture the electron as confirmed from steady state and time-resolved measurements establishing the role of Cu as an internal sensitizer for the charge carriers.