Several high-impact publications highlighting the work of EFRC:CST researchers hit the journals in early 2012. Below are short summaries of some of our most recent research findings:
1. Breakthroughs in OPV Research Achieved through Collaboration between EFRCs
A team of EFRC:CST researchers led by Xiaoyang Zhu published a report last year (Appl. Phys. Lett. 2011, 99, 083307) about a femtosecond electric field meter newly developed for probing ultrafast charge separation at donor/acceptor interfaces in organic photovoltaics (OPVs). In a collaboration with another EFRC based at Columbia University, Zhu’s team applied this method to obtain the first reported real-time observation of a multiexciton state generated from singlet fission in OPV films of pentacene (Science 2011, 334, 1541). This observation could be used to design more efficient solar cells in which multiple charge carriers could be harvested from the multiexciton state.
2. Model Systems of Interacting Polymer Chains Mimic Organic Photovoltaics
A team of EFRC:CST researchers led by David Vanden Bout and Christopher Bielawski designed a well-defined triblock copolymer based on poly(3-hexylthiophene), a model OPV material, that exhibits photophysical behavior similar to that of functional OPV films. Bielawski’s group synthesized the triblock polymers, and Vanden Bout’s group examined their photophysical properties specotrscopcially. The results, published in J. Phys. Chem. B (published online 1/31/2012), indicate that in the presence of a poor solvent, the two polythiophene chains within the triblock collapse to yield a material whose electronic spectrum mirrors that of a polythiophene film. This unique triblock polymer provides a model system for studying polythiophene spectroscopy in solution.
3. Storage Capacity of Lithium-Ion Batteries Increased through New Materials Synthesis
An EFRC:CST research team led by Brian Korgel and Keith Stevenson recently reported significantly improved Li-ion battery cycle performance and enhanced lithium storage capacity (7x increase) through the deposition of copper on amorphous silicon particles used as lithium-ion battery anodes (Chem. Mater. 2012, published online 3/8/2012). The copper coating creates an electronically conducting network among the clusters of silicon particles, thus enhancing the particles’ performance as a next-generation battery material. A new in situ Raman spectroelectrochemical technique developed by Stevenson’s group was used to observe the lithiation and delitiation of the particles in real time.
In a separate study, Stevenson’s group used a nanoparticle building block approach to create mesoporously ordered particles of TiO2(B), which could potentially replace traditional graphite anodes in Li-ion batteries. The EFRC:CST team found that the overall Li-ion insertion capacity of the mesoporously ordered TiO2(B) was markedly higher than that of TiO2(B) nanoparticles assembled without a template, because the mesoporous ordering resulted in better electrode/electrolyte contact and improved electron and ion transport through the particles (Langmuir 2012, 28, 2897). Both of these studies demonstrate the importance of meticulous materials design and architectural control for improving battery performance.