Available on-demand - S.EL13.07.31
Impact of Non-Halogenated Solvent Additives and Slot-Die Coating Processing on Perylene Diimide Based Active Layers Morphology
Francesco Tintori1,Audrey Laventure1,Gregory Welch1
University of Calgary1
Perylene diimide (PDI) derivatives are organic semiconductor that, among others, have been identified as one of the best classes of non-fullerene acceptors (NFAs) for organic photovoltaic (OPV) devices, with the best power conversion efficiency surpassing 10%. Recently, our group has developed a series of N-annulated PDI dimers, that have demonstrated excellent processability from all types of solvents, including environmentally friendly 2-Me-THF and 2-Me-anisole, and can achieve respectable performances in OPV devices.[2-4] The synthetic methods required to produce some of these have proven to be scalable and efficient, making them excellent candidates for the up-scaling of green printed electronic devices. We had previously identified one of said PDI dimers, with ethyl-hexyl side chains on the pyrrolic position, to be a suitable NFA for green solvent and air processed OPV.
This presentation will first discuss the rather unique self-assembly properties of this specific PDI NFA under the influence of processing solvent additives such as 1,8-diiodooctane (DIO), which can cause the crystallization of the molecular material in a polymeric matrix. This phenomenon was studied, and the aggregation effect was controlled under specific conditions using the benchmark polymer P3HT. To further investigate these findings and probe the phenomenon impact on a higher performing, and potentially scalable system, we identified a suitable medium band-gap benzodithiophene-quinoxaline polymer. The presentation will then focus on our effort to understand this system and translate it to scalable processing. First, diphenyl ether (DPE) was selected as a non-halogenated counterpart to DIO to make our system completely halogen-free, and effect of DPE on the PDI molecular material was studied. Then, a comparison of spin-coated and slot-die coated active layer films was made looking at film properties, morphology evolution and OPV device performance. We identified dependencies between these parameters and the selected coating method and worked with slot-die coating to obtain superior OPV results. The results obtained demonstrated that solvent additives might play an additional beneficial role in the device fabrication of printed organic active layers, highlighting the need of further exploration of additives with dual or even multiple functions to optimize the processing involved in green printed electronics.
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