PbS Quantum Dots Capped with Amorphous ZnS for Bulk
Heterojunction Solar Cells: The Solvent Effect
- Publication date
- Publisher
Abstract
In
this study, two distinct structures of PbS quantum dots (QDs)
are produced with amorphous ZnS as the capping material by successive
ionic layer adsorption and reaction. With methanolic solution, spherical
PbS QDs (∼5 nm) are embedded in the ZnS matrix (i.e., embedding
structure), exhibiting relatively large distance between the QDs.
With aqueous solution, irregularly shaped PbS QDs (<3 nm) blend
intimately with the ZnS medium (i.e., blending structure), showing
indiscernible QD spacing. This is attributed to a relatively low reactivity
of Pb<sup>2+</sup> ions in water, suppressing quantum dot growth in
the mesopores. Bulk heterojunction of mesoporous TiO<sub>2</sub> substrate
filled up with the blending configuration shows superior photovoltaic
performance to the embedding architecture, because of the small QD
size and close distance between the QDs