Sampath Dias

Electrical transport measurements of highly conductive carbon nanotube/poly(bisphenol A carbonate) composite

Acid-treated and pristine chemical vapor deposition grown multiwalled carbon nanotube (MWNT) and poly(bisphenol A carbonate) (PC) composites were prepared through a simple solution blending with varied nanotube weight fractions. The electrical conductivities of the composites can be described by the scaling law based on percolation theory with unprecedented high saturated ac conductivity of pristine nanotubes (σsat=1598.4 S cm−1, pc=0.19 wt %) and acid-treated nanotubes (σsat=435.4 S cm−1, pc=0.3 wt %), which correlates well with the dc behavior. We attribute the high saturated conductivities to managing the dispersions, rather than looking to have a well dispersed three-dimensional network thin film. The comparison was made between acid-treated nanotubes and pristine nanotube, both dispersed in PC at various loadings. It was found that the pristine nanotubes in PC possessed an even higher conductivity than the more evenly dispersed composites consisting of lightly acid-treated MWNT in PC.

Microconcentrator photovoltaic cell (the m-C cell): Modeling the optimum method of capturing light in an organic fiber based photovoltaic cell

We propose a new architecture as an alternative method when constructing organic photovoltaics (PVs) by addressing the best method to trap resonant light within the devices using fiber optics to concentrate light in the form of a microconcentrator cell (m-C cell). Our initial effort is to address how the m-C cells manage light absorption using a mathematical model that considers all the required parameters including the incident angle, meridional plane, cross sectional area, and path length. By knowing the materials,refractive index, we are able to calculate the optical angular input to achieve maximum absorption of resonant light. We also addressed the complexity of how changing refractive indices in a multilayer device can alter the angular dependence when considering the incident input light. The consequence is that we can ensure efficient absorption of resonant light in a thin film yet without issues of transmission losses which are evident in all other thin film organic PVs.

Fabrication, characterization, and optical modeling of a new architecture for organic photovoltaics: The vertically orientated stack device

We introduce a new architecture for organic photovoltaics based on vertically orientated devices. The fabrication, device characteristics, and an optical model of the stack organic photovoltaic (OPV) device are presented. This new architecture gives rise to an alternative to the common flat-panel structure, which was originally conceived for the first silicon devices. The OPV stack device has an increased short circuit current density, fill factor, and power-conversion efficiency, as opposed to the standard flat-panel device.