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ABSTRACT We present a study of optical and electronic properties of solutions and films based on the fungi-derived pigment xylindein, extracted from decaying wood and processed without and with a simple purification step (“ethanol wash”). The “post-wash” xylindein solutions exhibited considerably lower absorption in the ultraviolet spectral range and dramatically reduced photoluminescence below 600 nm, due to removal of contaminants most likely to be fungal secondary metabolites. The “post-wash” xylindein-based films were characterized by two orders of magnitude higher charge carrier mobilities as compared to “pre-wash” samples. This underlines the importance of minimizing contaminants that disrupt the conductive xylindein network in xylindein-based electronic devices. 

ABSTRACT We present on the optical and electronic properties of a fungi-derived pigment xylindein for potential use in (opto)electronic applications. Optical absorption spectra in solutions of various concentrations and in film are compared and are consistent with aggregate formation in concentrated solutions and films. In order to improve film morphology obtained by solution deposition techniques, an amorphous polymer PMMA was introduced to xylindein to form xylindein:PMMA blends. Current-voltage characteristics and hole mobilities extracted from space-charge limited currents were found to be comparable between pristine xylindein and xylindein:PMMA films. Side by side comparison of the photoresponse of pristine xylindein and xylindein:PMMA films at 633 nm revealed an increase in the photosensitivity in xylindein:PMMA films due to the improved morphology favouring enhanced charge generation. 

Organic semiconductor materials have recently gained momentum due to their non‐toxicity, low cost, and sustainability. Xylindein is a remarkably photostable pigment secreted by fungi that grow on decaying wood, and its relatively strong electronic performance is enabled by π–π stacking and hydrogen‐bonding network that promote charge transport. Herein, femtosecond transient absorption spectroscopy with a near‐IR probe was used to unveil a rapid excited‐state intramolecular proton transfer reaction. Conformational motions potentially lead to a conical intersection that quenches fluorescence in the monomeric state. In concentrated solutions, nascent aggregates exhibit a faster excited state lifetime due to excimer formation, confirmed by the excimer→charge‐transfer excited‐state absorption band of the xylindein thin film, thus limiting its optoelectronic performance. Therefore, extending the xylindein sidechains with branched alkyl groups may hinder the excimer formation and improve optoelectronic properties of naturally derived materials.