Organic-solvent-modified Polymer Solar Cells

Polymer solar cells based on conjugated polymers and fullerenes have been intensely studied for over a decade due to their advantages of easy fabrication, low cost, light weight, and flexibility in large-area applications. A rapid increase in power conversion efficiency from less than1%to over7%has been reported in the literature. Efficiency improvement has been facilitated through the control of morphology using solvent-treated buffer layers or additives in the preparation process of active layers.In this paper, we fabricated polymer solar cells based on P3HT and PCBM with the modification layer of PEDOT:PSS treated by different kinds of alcohol such as methanol, ethanol, glycol, glycerin, isopropyl alcohol and studied the organic solvent treatment on the performance of the solar cells. The cell with PEDOT:PSS treated by ethanol shows better performance than the cells treated by the other solvents. It has an open voltage of0.61V, a short circuit current of9.28mA/cm2, a fill factor of40.13%, and a power conversion efficiency of2.21%. The effect of annealing temperature on the surface morphology of the PEDOT:PSS interfaces treated by ethanol was also studied. The cell annealed at120℃exhibits a better performance. Its short circuit current, open voltage, fill factor, and conversion efficiency are9.52mA/cm2,0.62V,36.31%, and1.66%, respectively.On the other hand, three kinds of additives,1,3-propanedithiol,1,6-hexanedithiol,1,8-dibromooctane, were introduced into the active layers during the fabrication process in order to control the morphology and improve device performance. After annealing the cell with1,6-hexanedithiol displays a short-circuit current of6.65mA/cm2, a fill factor of42.36%, and an energy conversion efficiency of1.29%, which is the best among the cells.