The photovoltaic performance of CdTe quantum dots (QDs) sensitized solar cells (QDSSCs) as a function of tuning the band gap of
CdTe QDs size is studied. The tuning of band gap was carried out through controlling the size of QDs. Presynthesized CdTe QDs of radii
from 2.1 nm to 2.5 nm) were deposited by direct adsorption (DA) technique onto a layer of TiO2 nanoparticles (NPs) to serve as sensitizers
for the solar cells. The characteristic parameters of the assembled QDSSCs were measured under AM 1.5 sun illuminations. The
values of current density (Jsc) and overall efficiency (g) increase with decreasing CdTe QDs size, since the lowest unoccupied molecular
orbital (LUMO) levels shifts closer to vacuum level, which causes an increase in the driving force. Consequently the electrons’ injections
to the conduction band (CB) of TiO2 NPs become faster. The maximum values of Jsc (1105 lA/cm2) and g (0.190%) were obtained for
the smallest CdTe QDs size (2.10 nm). The open circuit voltages (Voc) varies slightly with the size of the CdTe QDs, however it is only
dictated by the CB level of TiO2 NPs and the VB of the electrolyte. Furthermore, the photocurrent response of the assembled cells to
ON–OFF cycles of the illumination indicates the prompt generation of anodic current.
2012 Elsevier Ltd. All rights reserved. |
