Nonplanar Perylene Diimides as Potential Alternatives to Fullerenes in Organic Solar Cells

Perylene diimides (PDIs) are attractive alternatives to fullerenes as electron transporters because of their optoelectronic properties, durability, and ease of synthesis. Belying this promise, devices that utilize PDIs as electron acceptors have low efficiencies. The primary deficiency in such cells is the low short circuit current density (JSC), which is traceable to the crystallinity of PDIs. Therefore, disrupting the crystallinity without adversely impacting the charge-transfer properties of PDIs is proposed as an important design principle. This has been achieved using a nonplanar perylene. In combination with a hole transporting polymer, a device efficiency of 2.77% has been achieved. A 10-fold increase in JSC is observed in comparison with a planar PDI, resulting in one of the highest JSC values for a solution processed device featuring a PDI. Indeed, this is one of the highest efficiencies for devices featuring a nonfullerene as the electron transporter.