Silver Reflector-Driven Light Harvesting Enhancement in Large Area Dye Sensitized Solar Cells

- Efficient light harvesting by absorber materials in large active area photovoltaic (PV) devices has always been a major challenge as some of the materials have smaller light absorption coefficients and their properties are impacted by scalability attempts. In addition, defects are more difficult to control when active area increases. In the present work, we demonstrated the positive impact of a silver reflecting surface consisting of a micrometer-thick, silver nanoparticles (Ag Nps)-based film on the glass side of platinum (Pt) counter electrode (CE). The films aimed to improve the light-harvesting ability of mesoporous TiO2 photoanodes on large-area dye sensitized solar cells (DSSCs). Although the power conversion efficiency (PCE) of large-area DSSC is lower in comparison to small-area DSSC, the PCE of the large-area Ag reflector based DSSC showed significant PCE improvement relative to reference DSSC. The enhancement is attributable to the improved light harvesting ability of photoanodes demonstrated from the increased short circuit current density (JSC) values of large-area Ag reflector based DSSC, as most of the unused incident light is reflected again due to the improved reflectivity of Pt CE via Ag reflecting film towards the photoanodes and is being reabsorbed by the dye sensitizers. This effect has been further confirmed by the electrochemical impedance spectroscopy (EIS) measurement, where resistances at different interfacial layers in DSSCs have been estimated. Hence, we report on a simple and efficient method of using Ag reflector films to enhance light harvesting in large-area DSSCs and paving the road towards improving performance of other large-area PV devices as well. Keywords: Large area DSSCs, DSSCs, Dye-sensitized solar cells, enhanced light harvesting, silver nanoparticles film