Polymer Solar Cell for Novel Applications: Device Physics, Processing and Stability

Due to dwindling sources of organic fuels and the potential opportunity to harvest some of the 84TW of solar power received by planet earth each day, solar cells are at the center of attention as potential candidates to solve the world's energy crisis. The high cost of inorganic solar cells in spite of their high power conversion efficiency (PCE) has been a major roadblock in their widespread acceptance. This is where the promise of low-cost, light-weight, flexible plastic solar cells comes into the picture. During the last decade organic solar cells have slowly risen to prominence as an alternative to traditional inorganic semiconductors for renewable energy production. The PCE has risen rapidly to reach 9.2% currently. In-spite of the huge promise, the fundamental organic material instability to moisture and oxygen is a cause of great concern. This will probably inhibit the use of such solar technology for terrestrial energy generation for grids.;This thesis looks at this critical question facing the OPV community. In this thesis, OPV have been looked at from a completely different point of view and novel applications like display and space have been explored. A novel technology called the Polarizing organic photovoltaic has been developed to integrate the PV technology with the LCD display technology resulting in potential reduction of backlight energy losses from 75% to 60%. A new device structure called the inverted quasi-bilayer was demonstrated as part of this work. Stability of OPV device for space applications has been explored. It has been shown that these devices are adequately radiation hard for space applications. The degradation mechanism for the devices under high energy radiation (as in space environment) has been suggested for the first time. Based on the understanding of the degradation mechanism, further device engineering efforts have lead to development of design guidelines to fabricate more radiation hard devices. The problem of device degradation was studied in more detail. It was established that although different processing conditions of the devices may lead to seemingly similar morphologies of the light absorbing layers; these morphologies have different characteristics of spatial and energetic distribution of trap states. This initial distribution of traps will play a critical role in determining the degradation rates of the light absorbing layers. It is hoped that as a result of this work, the scope of this promising technology will expand beyond just rooftop solar panels or portable flexible electronics. The fundamental study on degradation will help in understanding the nature and mechanism of this critical problem in more detail.