Perylene imides have been an object of research for 100 years and their derivatives are key n-type semiconductors in the field of organic electronics. While perylene diimides have been applied in many electronic and photonic devices, their use can be traced back to the first efficient organic solar cell. By functionalizing different positions of the in total 12 positions (four peri, four bay, and four ortho-positions) on the perylene core, perylene imides with significantly different optical, electronic and morphological properties may be prepared. Perylene imides and their derivatives have been used in several types of organic photovoltaics, including flat-, and bulk-heterojunction devices as well as dye-sensitized solar cells. Additionally perylene imides-based copolymers or oligomers play an important role in single junction devices. In this review, the relationship between the photovoltaic performance and the structure of perylene imides is discussed.

The photovoltaic parameters, i.e., the short-circuit current, open-circuit voltage and device fill factor, of bulk heterojunction solar cells that use perylene diimide (PDI) derivatives as electron acceptors are often far below the theoretically expected values for reasons still not entirely understood. This article demonstrates that the photovoltaic characteristics of blend films of regioregular poly(3-hexylthiophene) (rr-P3HT) and PDI molecules are improved upon using a core-alkylated PDI derivative instead of the often used N-alkylated PDI molecules. A doubling of the power conversion efficiency of P3HT:PDI solar cells by using the core-alkylated PDI derivative is observed leading to an unprecedented power conversion efficiency of 0.5% for a P3HT:PDI solar cell under AM1.5 solar illumination. Furthermore, the optical properties of the novel PDI derivative are compared to two standard exclusively N-alkylated PDI derivatives by steady-state and time-resolved photoluminescence spectroscopy in solution and solid state. The experiments reveal that aggregation in the solid state determines the photophysics of all PDI derivatives. However, the emission energy and excited state lifetime of the aggregates are clearly influenced by the alkyl-substitution pattern through its effect on the packing of the PDI molecules. X-ray diffraction experiments before and after thermal annealing of PDI:polystyrene and PDI:P3HT blends reveal subtle differences in the packing characteristics of the different PDI derivatives and, problematically, that P3HT ordering is suppressed by all of the PDI derivatives.

We present a new and versatile one-step synthesis of a series of small molecular chromophores based on cyclopentannulated polycyclic aromatic hydrocarbons (PAH). Easily available pyrene, anthracene, and perylene bromides serve as starting materials for the reactions. The formation of the five-membered ring is achieved by the straightforward palladium(0)-catalyzed carbannulation with various substituted acetylenes. This approach is applicable either to single or multiple annulation procedures leading to hitherto inaccessible PAH topologies. According to the resulting products of the diverse reactions, a mechanistic explanation is proposed. UV/Vis absorption as well as cyclovoltammetric measurements were performed for characterization demonstrating the value of this annulation technique. Optical absorptions of up to 780 nm and absorption coefficients ranging from 8000 to 34 000 M⁻¹ cm⁻¹ were detected.