INTERFACE LAYER MODIFICATIONS USING POLYELECTROLYTES FOR HIGH EFFICIENCY ORGANIC SOLAR CELL

Abstract

Considering the present world energy consumption and the exponential growth in human population, the growing energy need has to be mollified by the use of renewable sources of energy such as solar energy. Development is necessary but not at the cost of the future generations. The need of the hour is sustainable development. Thus, concerns about global warming and diminishing fossil fuel reserves have accelerated the search for low cost sources of renewable energy. Organic photovoltaics (OPVs) could be one such source. The investigation in this thesis takes a step in this direction. The solar cells investigated in this thesis are BHJ solar cells. Fabrication of such cells involve etching of the substrates, preparation of the active material and buffer layer solutions, cleaning of the substrates, coating and deposition of the materials over the substrate. Finally once these solar cells are fabricated, J-V characterization of these cells are carried out to determine the device parameters- power conversion efficiency (PCE), open circuit voltage (VOC), fill factor (FF) and short circuit current density (JSC). In this thesis we have focused on the interface layers in conventional and inverted organic solar cells. In case of conventional devices, we have tried to replace PEDOT:PSS by MoO3 layer and whereas in case of inverted devices, we have applied a polyelectrolyte based approach for modifying the ZnO interface layer. Herein, we have used solution based approach for MoO3 and demonstrated that PEDOT:PSS can be successfully replaced by solution processed MoO3. For the modification of interface layer in case of inverted devices we have used the combination of zinc oxide and polyelectrolyte viz. ZnO-PDADMAC and ZnO-PSS nanocomposite. Both of these combinations have shown remarkable increase in the device parameters such as- JSC and η. However, the Zno-PDADMAC nanocomposite has shown a huge increase of ~ 22 times in device efficiency. These results have been discussed in detail in this thesis.