Speaker
Description
Different from inorganic thin-film solar cells relying on stacked donor (p-type doped) and acceptor (n-type doped) layers of the same material, the photoactive layer of polymeric organic photovoltaics (OPVs) make use of two distinct polymer donor and molecular acceptor materials. These are mixed at the nanoscale in a bulk heterojunction thin film to capitalize on the very fast relaxation rates and short diffusion lengths of electron-hole (e-h) pairs in organic soft matter. While the root cause for short e-h lifetimes in organic semiconducting polymers is still an intriguing subject of debate, a lot of the underlying photophysics can be understood by utilizing, in an OPV device, novel 'smart' molecular acceptors with precisely controlled optical properties which can act as 'photo-switches' turning 'on' and 'off' the e-h pair diffusion and dissociation through a change in their conformation.
Our research addresses this challenge by fabricating specific bi-functional systems based on molecular nanoclusters. Metallic nanoclusters containing a deterministic number of metal atoms sit at the intersection between molecular materials and metal nanoparticles, and they are uniquely suited to this end. Our approach utilizes a carbonate-templated Ag₂₀ nanocluster, designed in-house, which has been surface-functionalized with azobenzene derivatives to impart a photo-switchable behavior. The precise atomic structure of the functionalized nanocluster was confirmed by single-crystal X-ray diffraction (SCXRD). Not only this tailored ligand shell enables optical 'on'/'off' control but also confers significant photostability, greatly slowing the oxidation of the Ag₂₀ silver core. Reversible trans-cis isomerization was monitored via ultraviolet-visible (UV-Vis) optical spectroscopy, showing near-quantitative conversion and robust cyclability. The ability to optically modulate the cluster’s electronic properties highlights its potential as a molecular switch for photovoltaic activity in OPVs. Current work focuses on exploring the solid-state properties and integrating C₆₀/C₇₀ fullerenes to realize a single-component switch-acceptor hybrid material.
| Keyword-1 | Determinic molecular clusters |
|---|---|
| Keyword-2 | Organic solar cells |
| Keyword-3 | Optical switching |