The Salleo Group (click here to see the Salleo Group review) has recently published a paper, “A general relationship between disorder, aggregation and charge transport in conjugated polymers“, regarding an interesting discovery.
Let’s face it, due to their cheap & easy to produce nature, organic solar cells will, at some point, take the crown from Crystalline Silicon cells. The low efficiency of organic cells is still a big drawback but, perhaps with this recent development, we will see significant improvements.
A relatively new fact about polymer solar cells (aka plastic solar cells) is that the cells show improved performance when the material is less orderly. This is a big game changer as scientists have been all along trying to mimic the perfect molecule structure of crystalline silicon to achieve competitive performance values while using polymer. The Salleo team used X-rays to investigate this fact. They noticed very small crystals in the material connected by long polymer chains. These long polymer chains & small crystals, beads in a necklace per the team’s analogy, allowed the less orderly material to have much higher mobility for electrons. This, in return, improves the performance.
The graph below explains the team’s findings about electron mobility with respect to structure. The semi-crystalline materials are demonstrated in red, less orderly materials are in black, others in orange. The less orderly materials clearly show much better electron mobility.
To learn more about this effort, please click here to download the paper, “A general relationship between disorder, aggregation and charge transport in conjugated polymers“.