Research Interests:

• Design, synthesis, and development of organic semiconductor materials and processes for flexible, stretchable optoelectronic application
• Design and development of materials systems for alternative energy applications with a focus on photovoltaics
• Design and development of materials platforms to enable high-performance flexible battery electrode systems
• Exploration of structure-process-property relationships in organic and hybrid pi-conjugated materials to enable development of a “tool-box” for the design of materials with enhanced performance attributes 
• Elucidation of conjugated polymer thin film nanostructure/microstructure evolution and its correlation with macroscopic charge transport
• Multifunctional, hybrid organic/inorganic nanocomposites for optical, electrical, catalytic, and dielectric applications
• Harness nature’s ability to template the growth of ordered structures on the nanoscopic through macroscopic scales to develop “green” electronics

The Reichmanis Group works at the interface of chemical engineering, chemistry, materials science, optics, and electronics spanning the range from fundamental concept to technology development and implementation. Research interests include the chemistry, properties and applications of materials technologies for electronic and photonic applications, with particular focus on polymeric and nanostructured materials for advanced technologies.

Design, synthesis and characterization of organic semiconductors

Although significant progress has been made, organic semiconducting polymers typically have low charge carrier mobility, low oxidation stability and a relatively large bandgap relative to their inorganic counterparts. From a molecular perspective, intra- and inter-molecular π-orbital overlap (or π – π stacking) determines the charge transport performance. We are engaged in studying the effects of molecular co-planarity, intra-molecular charge transport and electron-withdrawing substitution on the optical and electronic properties of candidate polymers with the aim of facilitating their field-effect charge transport and photovoltaic performance.

Fundamental structure-property-process relations in conjugated polymer semiconductors

To take full advantage of organic semiconductor technology, solution processed materials are required for conventional mass printing applications. The development of viable active polymer materials for such applications requires not only the development of relevant chemistries, but also the development of compatible device fabrication processes. We are developing efficient processing techniques to manipulate and control the micro-/macro-structure of the thin films, and investigating how the resultant structure impacts macroscopic charge transport within the material. Techniques such as absorption and vibrational spectroscopy, atomic force microscopy, x-ray diffraction and electrical measurements of thin films have been employed to understand relationships between molecular structure, thin film architecture, optical properties and macroscopic charge transport in organic/polymer/hybrid semiconductor materials. Features extracted from of microstructural data is analyzed through image analysis, peak fitting, and other techniques from the rapidly growing field of data science. Efforts to elucidate the role of interfaces are also in progress.

Processing dependent morphology-performance relationships in organic photovoltaic cells

Phase separation and crystallization into desirable bulk heterojunction morphologies through process optimization are effective ways to increase the power-conversion efficiency of an organic photovoltaic cell. Process parameters such as solvent boiling point/volatility, solubility parameters of both the active materials and deposition solvents, thermal and/or solvent vapor annealing have a profound impact on the morphology of the active layer, which influences solar cell performance. We are engaged in investigating how process parameters affect blend morphology and thus device performance. For instance, Hansen solubility parameters and Spano’s model are employed to systematically understand the effects of processing on the morphology and thus optoelectronic properties of the photovoltaic cells.

Flexible batteries

For the creation of practical and aesthetic electronic devices, flexible batteries are considered as a promising solution, owing to their potential to adapt to mechanical stress and thereby shape transformation. Furthermore, to keep pace with the recent trends, considerable efforts have been made to develop the facile, robust flexible lithium-ion batteries based on not only developing the advanced materials, but also constructing the newly flexible, systematic platforms. For example, there has been focus on the development of flexible batteries adopting soft materials such as polymer electrolytes, nano-sized active materials, and highly patterned, flexible current collectors, as well as using flexible, elaborate frames like a cable-type, serpentine interconnect, or origami structure. Despite of these intensive efforts, conjugated conducting polymers have not been extensively investigated. Our research explores physiochemical phenomena associated with conjugated polymers in battery electrode systems. We will use our fundamental insight to design and build robust, flexible electrode frames.

Biomaterials

Biomaterials such as PSLG and cellulose nanocrystals are being explored for use in "green" electronics. Cellulose nanocrystals are rigid, rod-like particles that form a lyotropic liquid crystal in water. If these particles can enforce long-range order in semiconducting polymers such as P3HT, we expect that the charge carrier mobility will increase due to improved pi-pi stacking. Other cellulose derivatives such as cellulose nanofibrils show promise in paper-based battery applications as well.