The interlayer materials used in non-fullerene based solar cells are reviewed and the peculiar mechanisms operating in these systems are discussed.

We report on the photophysical characterization of two solution-processable red-emissive perylene diimide molecules and on their use in fully solution assembled OLEDs. The two emitters contain sterically hindered aromatic naphthalene or acenaphthene substituents on the perylene core. These fused rings limits the perylene diimide intermolecular π–π interactions in the solid state due to highly sterically hindered effects, while preserving an extended conjugation between the substituents and the perylene core. Indeed, these features generate a broad absorption for both perylene derivatives along with an efficient red and deep red emission in the solid state for the PDIs with naphthalene and acenaphthene, respectively. The performances of both emitters were tested on OLEDs, where the active layer is a film of bulk PDI, fabricated by simple solution processing. The devices with acenaphthene-substituted perylene diimide provide deep red electroluminescence with emission wavelength at 690 nm, CIE coordinates of (x = 0.69, y = 0.29) and show the best efficiency reported so far for OLED based on PDI fluorescent emitters.

Two new organic sensitizers for dye solar cells containing a sterically hindered moiety have been synthesized. The introduction of a 3,4-dibutyl-thiophene ring into D–π–A dyes reduces the sensitizer aggregation and allows the preparation of solar cells with PCE of 7.17% and 6.27% without the use of coadsorbant agents.