Melanin denotes a variety of mammalian pigments, including the dark electrically conductive eumelanin and the reddish, sulfur-containing, pheomelanin. Organic (bio)electronics is showing increasing interests in eumelanin exploitation, e.g., for bio-interfaces, but the low conductivity of the material is limiting the development of eumelanin-based devices. Here, for the first time, we report an abrupt increase of the eumelanin electrical conductivity, revealing the highest value presented to date of 318 S/cm. This result, obtained via simple thermal annealing in vacuum of the material, designed on the base of the knowledge of the eumelanin chemical properties, also discloses the actual electronic nature of this material's conduction.

The growing interest toward biocompatible and bioinspired materials is boosting the investigation and the engineering of natural products as active components in electronic devices. The human pigment melanin, and particularly its subgroup composed by the eumelanins, the black‐brown pigments derived from the oxidative polymerization of L‐3,4‐dihydroxyiphenylalanine (l‐DOPA) via 5,6‐dihydroxy‐indole intermediates are increasingly emerging as valuable candidates for organic (bio)electronics applications. Capitalizing on a recently developed protocol to prepare high quality eumelanin coatings, this paper reports herein the design and the integration of standard commercial poly(3,4‐ethylenedioxythiophene) with the poly(styrenesulfonate) (PEDOT:PSS) with eumelanin pigment. The new blend has made it possible to obtain a water stable quite transparent thin film, able to operate as an electrode for organic devices, complementing the PEDOT:PSS conductivity with the peculiar eumelanin properties, including adhesion, water stability, and ionic–electronic conductivity. As proof of concept, an unprecedented indium tin oxide‐free organic light emitting diode implementing an eumelanin–PEDOT layer as the anode is fabricated and characterized.

The oxidative polymerization of 5,6‐dihydroxyindoles and related hydroxyindoles at pH<3 is diverted from the usual eumelanin‐forming pathway to produce mixtures of symmetric and asymmetric triazatruxenes (TATs), which could be separated and characterized for their opto‐electronic properties with the aid of TD‐DFT calculations. Data showed that the asymmetric isomers exhibit higher fluorescence quantum efficiencies, lower HOMO–LUMO gaps, better film homogeneity, and a more definite aggregation behavior than the symmetric counterparts, suggesting promising applications in organic electronics. The enhanced luminance exhibited by the OLED devices fabricated with blends of the synthesized TATs in poly‐9‐vinylcarbazole confirmed the potential of the asymmetric skeleton as new versatile platform for light‐emitting materials.

Highly sensitive alternate current (ac) impedance measurements with variable temperature have been performed to investigate the optical and electrical failure mechanisms during the glass transition phenomena in the archetypal ITO/TPD/Alq3/Al organic light emitting diode (OLED) structure. Since the device degradation is mainly related to the lower glass transition temperature (Tg) of the N,N′-Bis(3-methylphenyl)-N,N′-diphenylbenzidine (TPD), this study is focused on the frequency response of thin TPD films approaching the glassy region. The related experimental data are discussed in the framework of the universal dielectric response model. By ac measurements, TPD glass transition temperature is located and temperature regions with different OLED behaviors are evidenced. The relation between the behaviors of TPD frequency response and of the OLED electro-optical response, while the temperature approaches the glass transition region, is discussed.

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