Designing Liquid Crystalline Ligands for Increased QD Photovoltaic Efficiency

High-efficiency quantum dot (QD) solar cells use nanoparticles to absorb incident light. QD photovoltaics are potential candidates for use in space missions due to their long lifetimes and stable photonic properties under high photon flux, however, one limitation of this technology is the loss of efficiency due to inter-dot energy transfer.In this project, we tried to tune the spacing between QDs by using mesogenic ligands (rod-like molecules attached to the particle by a flexible alkyl chain) to decrease the loss of energy. This strategy will provide an effective route towards improving the functional and structural characteristics of QD hybrid devices.
In the specific case of semiconducting QD nanoparticles, the photophysical properties are strongly tied to surface conditions. In a recent publication, we found that mesogenic ligand surface attachment can promote long-term QD photo-stability. The mesogenic ligands reduced inter-dot energy transfer, produced stable recombination rates and steady emission color over more than an hour of continuous photo-excitation. These effects were more prominent with a longer ligand attachment chain. After this, we present a new ligand design toward the goal of high efficiency.