Biocompatibility tests and a study of the electrical properties of thin films prepared from six electroactive polymer ink formulations based on poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) were performed. The aim was to find a suitable formulation of PEDOT:PSS and conditions for preparing thin films in order to construct printed bioelectronic devices for biomedical applications. The stability and electrical properties of such films were tested on organic electrochemical transistor (OECT)-based sensor platforms and their biocompatibility was evaluated in assays with 3T3 fibroblasts and murine cardiomyocytes. It was found that the thin films prepared from inks without an additive or any thin film post-treatment provide limited conductivity and stability for use in biomedical applications. These properties were greatly improved by using ethylene glycol and thermal annealing. Addition or post-treatment by ethylene glycol in combination with thermal annealing provided thin films with electrical resistance and a stability sufficient to be used in sensing of animal cell physiology. These films coated with collagen IV showed good biocompatibility in the assay with 3T3 fibroblasts when compared to standard cell culture plastics. Selected films were then used in assays with murine cardiomyocytes. We observed that these cells were able to attach to the PEDOT:PSS films and form an active sensor element. Spontaneously beating clusters were formed, indicating a good physiological status for the cardiomyocyte cells. These results open the door to construction of cheap printed electronic devices for biointerfacing in biomedical applications. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 1121-1128, 2018.

The singlet fission (SF) process discovered in bis(thienyl) diketopyrrolopyrroles (TDPPs) can boost their potential for photovoltaics (PV). The crystal structures of TDPP analogs carrying n-hexyl, n-butyl, or 2-(adamant-1-yl)ethyl substituents are similar, but contain increasingly slipped stacked neighbor molecules. The observed SF rate constants, k SF , (7 � 4), (9 � 3) and (5.6 � 1.9) ns À 1 for thin films of the three compounds, respectively, are roughly equal, but the triplet quantum yields vary strongly: (120 � 40), (160 � 40) and (70 � 16), respectively. The recent molecular pair model reproduces the near equality of all three k SF at the crystal geometries and identifies all possible pair arrangements in which SF is predicted to be faster, by up to two orders of magnitude. However, it is also clear that the presently non-existent ability to predict the rates of processes competing with SF is pivotal for providing a guide for efforts to optimize the materials for PV.

Ethyladamantyl solubilization side groups were found to induce π−π interactions between the conjugated cores in soluble diketopyrrolopyrrole derivatives.

No abstract

In this work, we investigated diketopyrrolopyrrole (DPP) derivatives as potential donor materials for fullerene:DPP solar cells. The derivatives 3,6-bis­(5-(benzofuran-2-yl)­thiophene-2-yl)-2,5-bis­(2-ethylhexyl)­pyrrolo­[3,4-c]­pyrrole-1,4-dione (DPP­(TBFu)2) and 3,6-bis­(5-(benzothiophene-2-yl)­thiophene-2-yl)-2,5-bis­(2-ethylhexyl)­pyrrolo­[3,4-c]­pyrrole-1,4-dione (DPP­(TBTh)2) were modified by introducing a nitrogen atom into the terminal moiety of the molecule. Our quantum-chemical calculations predicted that this modification would increase the rigidity of the molecular structure and increase the ionization potential relative to the original DPP derivatives. The higher ionization potential primarily supports an enhancement in the open circuit voltage, and a more rigid molecular structure will contribute to reduced nonradiative losses. We experimentally verified the fullerene:DPP solar cell concept based on the coincidence of a smaller driving force for charge separation at the donor/acceptor interface and the crystallinity of the studied DPP derivatives for preparing effective photovoltaic devices. The reduction of the driving force for charge separation could be overcome by more structured/packed donor DPP materials; the delocalization of electrons and holes in such structured materials improves charge separation in OPV devices. Using wide range of experimental methods, we determined the parameters of the studied DPP materials with PC70BM in thin films. This work contributes to practical applications by verifying the concept of this organic solar cell design.