Additive induced crystallization of a twisted perylene diimide dimer within a polymer matrix

Development of Tetrameric N-Annulated Perylene Diimides Using "Click" Chemistry

Herein, we report the design, synthesis, and characterization of two novel N-annulated perylene diimide (NPDI) tetramer arrays that were developed using copper catalyzed alkyne-azide cycloaddition. Despite the optoelectronic properties of both tetramers being nearly identical, the two tetramers exhibited very different molecular geometries. The twisted spirobifluorene NPDI tetramer (sbfNPDI₄ ) was found to have an extended and flexible geometry, while the planar pyrene NPDI tetramer (pyrNPDI₄ ) exhibited a highly congested and conformationally locked geometry. Organic photovoltaic devices were constructed to demonstrate the use of both new compounds as electron acceptor materials, where slightly higher power conversion efficiencies were achieved with pyrNPDI₄ than sbfNPDI₄ . This study highlights the viability of using "click" chemistry as a facile synthetic strategy towards the development of new multicomponent perylene diimide materials for organic electronic applications.

Hybrid Tetrameric Perylene Diimide Assemblies

Organic photovoltaics have found utility as indoor light recycling devices providing an opportunity for the sustainable powering of IoT sensors and related smart electronics. In the report, two organic π-conjugated molecules consisting of four perylene diimide (PDI) chromophores each are presented and used as non-fullerene acceptors in indoor photovoltaic devices. The new materials consist of a dimeric N-annulated PDI core with single PDIs grafted onto the pyrrolic N-atom positions of the core. Compounds PDI₄ e and PDI₄ i are PDI tetramers and differ with PDI₄ e having the terminal N-annulated PDI with pyrrolic N-atom distal to the core and PDI₄ i having the terminal N-annulated PDI with pyrrolic N-atom proximal to the core. The structural and optoelectronic properties were investigated using NMR spectroscopy, optical absorption and emission spectroscopy, and cyclic voltammetry. The compounds exhibit typical optical signatures for PDIs but notable is that the addition of grafted PDI molecules prevents significant aggregation of the dimeric PDI core, as compared to a reference dimer. Use as non-fullerene acceptors in ternary bulk-heterojunction blends with the polymer FBT and fullerene PC₆₁ BM lead to increased open-circuit voltages and power conversion efficiencies upwards of 13.7 % at 2000 lux light intensity.

Indoor Photovoltaics: Photoactive Material Selection, Greener Ink Formulations, and Slot-Die Coated Active Layers

Strong visible light absorption is essential to achieve high power conversion efficiency in indoor organic photovoltaics (iOPVs). Here, we report iOPVs that exhibit high efficiency with high voltage under excitation by low power indoor lighting. Inverted type organic photovoltaic devices with active layer blends utilizing the polymer donor PPDT2FBT paired with fullerene, perylene diimide, or ring-fused acceptors that are 6.5-9.1% efficient under 1 sun are demonstrated to reach efficiencies from 10 to 17% under an indoor light source. This performance transcends that of a standard silicon photovoltaic device. Moreover, we compared iOPVs with active layers both spin-cast and slot-die cast from nonhalogenated solvents and demonstrate comparable performance. This work opens a path towards high-efficiency iOPVs for low power electronics.

Perylene Diimide Based Organic Photovoltaics with Slot-Die Coated Active Layers from Halogen-Free Solvents in Air at Room Temperature

Herein, we investigate the role of processing solvent additives on the formation of polymer-perylene diimide bulk-heterojunction active layers for organic photovoltaics using both spin-coating and slot-die coating methods. We compare the effect of 1,8-diiodooctane (DIO) and diphenyl ether (DPE) as solvent additives on the aggregation behavior of the non-fullerene acceptor, N-annulated perylene diimide dimer (tPDI₂N-EH), in neat films and blended films with the benzodithiophene-quinoxaline (BDT-QX, QX-3) donor polymer, processed from toluene in air. DIO processing crystallizes the tPDI₂N-EH acceptor and leads to the decreased solar cell performance. DPE processing has a more subtle effect on the bulk-heterojunction morphology and leads to an improved solar cell performance. A comparison of the spin-coating vs slot-die coating methods shows that the effect of DPE is prominent for the slot-die coated active layers. While similar device power conversion efficiencies are achieved with active layers coated with both methods (ca. 7.3% vs 6.5%), the use of DPE improves the film quality when the slot-die coating method is employed.