Paper presented to the 3rd Southern African Solar Energy Conference, South Africa, 11-13 May, 2015.
In this paper, the enhancements in the light harvesting of photoactive materials by fabricating hierarchical structures were examined using electrospinning. Electrospinning due to ease of processing, has become an attractive technique for fabrication of polymer fibers ranging from sub-microns to few nanometers. Here we present a uniform network structure obtained by electrospinning of a conducting polymer blend; poly (3 hexyl thiophene) (P3HT) and phenyl-C61-butyric acid methyl ester (PCBM). The study was carried out by varying the processing parameters like voltage applied, flow rate, tip-to-collector distance while solution concentrations, needle gauge, fabricating time were kept constant. Scanning electron microscopy and optical microscopy were used to evaluate the morphology changes with respect to varying processing conditions. The dictating parameters on the evolving structure were high voltage, tip to collector distance and solvent used. It was observed that there was an upper and lower limit to the voltage applied, and flow rate used, to get uniform network. Moving away from either of the limits leads to irregular deposition. Optical properties due to structured architecture showed enhancement in the internal reflection and in turn leading to higher light absorption. Opto-electrical characteristics of these devices showed higher order of response in comparison to standard film devices. This structure was evaluated for better light harvesting, and enhanced pathways for charge transportation as active layer architecture in an organic photovoltaic devices. Hence a step towards better light and charge management is possible by tuning the morphological structures of photoactive materials with optimized process parameters by electrospinning.
