Lifetime and Efficiency of Dye-Sensitized Polymer Solar Cells
Kyle J Bandaccari, Grace E. Chesmore, Parisa Tajalli-Tehrani Valverde
Faculty Mentors: Brian J. McNelis and Richard P. Barber, Jr.
The scope of applications of current silicon solar cells is limited by high production cost, low flexibility (both literally and figuratively), and long production timelines. However, current research-grade organic solar cells approach neither the efficiency nor long-term stability of their inorganic counterparts. The efficiency patterns of organic solar cells are well studied, but few reports of long-term stability exist in the literature. This study aims to investigate the effects of dyes on the lifetime of the model PCBM:P3HT active layer.
A novel synthetic dye was incorporated into device active layers at concentrations ranging from 2 to 10 wt. % with respect to PCBM. We observe increases in both lifetime and efficiency in dye-sensitized PCBM:P3HT devices when compared to unaltered devices of the same type. Optimization of both figures appears to occur at dye loadings just above 5 wt. %. Addition of the dye may prolong the time before irreversible fullerene or polymer self-aggregation occurs, but only at particular concentrations. Additional investigations via time-dependent Ultraviolet-Visible Spectroscopy (UV-Vis), Atomic Force Microscopy (AFM), and optical microscopy characterize reorganization patterns of the bulk heterojunction which may be responsible for device degradation in ambient conditions. UV-Vis data characterize the layers' absorption properties over time as degradation occurs, allowing for calculation of lifetime via an alternate (non-electrical) route. AFM and optical microscopy images indicate changes in active layer surface morphology which may disrupt charge separation and transfer.