This EArly-concept Grants for Exploratory Research (EAGER) grant provides funding for the development of electropolymerized light absorbing layers and charge transfer complexes between semi-conducting polymers and functionalized carbon nanotubes. These materials and structures are targeted towards use in thin-film organic photovoltaics, a technology that may enable deployment of inexpensive, flexible photovoltaic modules for a wide range of applications. In this project, monomers with low solubility but advantageous light absorption properties will be electropolymerized to form 50-300 nm films. Electrodeposition of soluble monomers can induce high pi-pi stacking order normal to the electrode surface which creates favorable molecular alignment for thin, light-absorbing films. The films will be interrogated for their optical and charge transport properties and processing-structure-property relationships will be developed to guide the fabrication of high performance films that have broad-spectrum light absorption and high charge mobility. Porous carbon nanotube mats will be impregnated with electrodeposited polymer to create donor-acceptor assemblies. The nanotubes may be surface-functionalized to tune the energy level differences between the polymer electron donor and nanotube electron acceptor for efficient charge transfer between phases, a critical step in the operation of organic photovoltaics.
If successful, the results of this research will lead to improvements in organic photovoltaic active layer processing and a deeper understanding of the optical and electrical properties of electropolymerized polymers. The primary goal of this work is to determine the potential of a new processing method for photovoltaic active layers and to measure the key light absorption and charge transport attributes of these materials. Determining the process parameters and critical materials properties to achieve the objectives of this work will help to reduce the cost and widen the possible materials set for organic photovoltaic devices. The work will also contribute to fabrication of optoelectronic thin films for other applications such as polymer electronics.
This EArly-concept Grants for Exploratory Research (EAGER) grant provided funding to explore new ways to make thin polymer films that absorb light and transport electrodes. These materials and structures are targeted towards use in thin-film organic photovoltaics, a technology that may enable deployment of inexpensive, flexible photovoltaic modules for a wide range of applications. The light absorbing layers were deposited on surfaces from solution using electric potential in a process similar to electroplating. This type of deposition is fast, films were formed in less than 1 min, and allowed us to control the thickness and structure of the film exactly. Because the polymer was deposited from the monomer state, porous structures, such as carbon nanotube mats, could be infiltrated with monomers to form a dense donor-acceptor composite structure. We have focused on the basic materials processing and molecular structure issues in this work. We have found that the solvent, current, and deposition conditions play a key role in the alignment of the material and its order through the film. We have also been able to co-deposit organic films and fullerenes to make donor-acceptor structures. The detailed molecular alignment and spectroscopic studies undertaken have yielded a picture of how the material obtains its properties for light adsorption and charge transport. We are continuing to use the processing technology and insights developed through this grant to impact other technologies such as flexible displays and other electronic devices that can be made from electron conducting polymers. The results of this research have lead to improvements in organic photovoltaic active layer processing and a deeper understanding of the optical and electrical properties of electropolymerized polymers. The primary goal of this work has been to determine the potential of a new processing method for photovoltaic active layers and to measure the key light absorption and charge transport attributes of these materials. The processing parameters and critical materials properties to achieve the objectives of this work have helped to reduce the cost and widen the possible materials set for organic photovoltaic devices and other types of polymer electronic technologies.
