Six new N-annulated perylene diimide molecules are reported with varied pyrrolic N-atom sidechains. Impact on optoelectronic and physical properties is investigated.

The synthesis of 6,11-bis-cyano N-H functionalized perylene diimide is reported. Electron withdrawing cyano groups were installed to counter the electron donating cyclic amine moiety with retention of functionality. Solution-processed, air-stable...

Solution-processable organic solar cells (OSCs) have the potential to offer a source of low-cost renewable energy with low-energyintensive processing, have lightweight and flexible features, and power conversion efficiency (PCE) values of 19%. [1,2] The most efficient OSC devices are based on the bulk heterojunction (BHJ) structure composed of nanoscale intermixed continuous networks of an electron-donating conjugated polymer and a nonfullerene electron-accepting small molecule, together with anode and cathode interlayers (CILs) to improve charge carrier transport and collection in the device. [3,4] In bottom-anode top-cathode device configuration, PEDOT:PSS is the most common anode interlayer, which is deposited on top of the indium tin oxide (ITO) transparent electrode. In this configuration, the CIL would therefore be deposited on top of the organic BHJ to modify the electrode work function, such that OSC device performance would be increased as a result of the energy barrier between the metal electrode and the active layer being decreased. [5][6][7][8] To date, organic compounds have been widely applied as interlayers, and benchmark CILs for conventional OSC structure utilize the PFN-Br polymer [9] and small molecules based on perylene diimide (PDI) derivatives, such as those with polar amino N-oxide groups (PDINO) [10] or aliphatic amine groups (PDINN). [11] The polar groups endow the molecules with good solubility in methanol, a processing solvent that does not destroy the underlying organic photoactive layer. [4] In terms of better reproducibility, reduced synthetic steps, and well-defined structures, small-molecule interlayers exhibit intrinsic advantages over polymeric materials, which position PDI-based CILs as excellent candidates for future industrial applications of OSCs. [12,13] PDIs also have high electron mobility, strong optical absorption, suitable energy levels, and stability. [14] In addition, they can be easily functionalized to tune the work function of the electrode. [13,15] Through chemical modification, the electronic and morphological features of the applied PDI in the interlayer film can be adjusted to deliver better performance in the OSC device. Recently, some works featured the use of bay-substituted PDIs as CILs in OSCs. Wang et al. reported the synthesis of three bay-substituted PDIs and their application as CILs in OSCs, with performance of 16% when combined with PM6:Y6. [16] Our group also reported the use of PDI compounds containing NH groups functionalized at the bay region as an interlayer in OSCs, slot die coated from ethanol, with device performance above 10%. [17] Here, we present the application of a series of bay positionsubstituted N-annulated PDI derivatives as interlayers for OSCs. These N-PDIs possess well-defined structures and good film-forming ability on top of the organic photoactive layer,

The synthesis, characterization, and photovoltaic performance of three N-annulated perylene diimide dimers with benzyl based side-chains is reported.

Roll-to-roll coating of conventional organic photovoltaic architectures in air necessitates low work function, electron-harvesting interlayers as the top interface, termed cathode interlayers. Traditional materials based on metal oxides are often not compatible with coating in air and/or green solvents, require thermal annealing, and are limited in feasibility due to interactions with underlying layers. Alternatively, perylene diimide materials offer easily tunable redox properties, are amenable to air coating in green solvents, and are considered champion organic-based cathode interlayers. However, underlying mechanisms of the extraction of photogenerated electrons are less well understood. Herein, we demonstrate the utilization of two N-annulated perylene diimide materials, namely, PDIN-H and CN-PDIN-H, in air-processed conventional organic photovoltaic devices, using the now standard PM6:Y6 photoactive layer. The processing ink formulation using cesium carbonate as a processing agent to solubilize the perylene diimides in suitable green solvents (1-propanol and ethyl acetate) for uniform film formation using spin or slot-die coating on top of the photoactive layer is critical. Cesium carbonate remains in the film, creating hybrid organic/metal salt cathode interlayers. Best organic photovoltaic devices have power conversion efficiencies of 13.2% with a spin-coated interlayer and 13.1% with a slot-die-coated interlayer, superior to control devices using the classic conjugated polyelectrolyte PFN-Br as an interlayer (ca. 12.8%). The cathode interlayers were found to be semi-insulating in nature, and the device performance improvements were attributed to beneficial interfacial effects and electron tunneling through sufficiently thin layers. The efficiencies beyond 13% achieved in air-processed organic photovoltaic devices utilizing slot-die-coated cathode interlayers are among the highest reported so far, opening new opportunities for the fabrication of large-area solar cell modules.