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Abstract The conductive polymer poly(3,4-ethylenedioxythiphene):poly(styrenesulfonate) (PEDOT:PSS) is widely used in organic electronics and printed electronics due to its excellent electronic and ionic conductivity. PEDOT:PSS films exhibit anisotropic conductivities originating from the interplay of film deposition processes and chemical structure. The previous studies found that high boiling point solvent treated PEDOT:PSS exhibits an anisotropy of 3–4 orders magnitude. Even though both the in-plane and out-of-plane conductivities are important for the device performance, the out-of-plane conductivity is rarely studied due to the complexity with the experiment procedure. Cellulose-based paper or films can also exhibit anisotropic behavior due to the combination of their intrinsic fibric structure and film formation process. We have previously developed a conductive paper based on PEDOT:PSS and cellulose which could be used as the electrodes in energy storage devices. In this work we developed a novel measurement set-up for studying the anisotropy of the charge transport in such composite materials. A tool with two parallel plates mounted with spring loaded probes was constructed enabling probing both lateral and vertical directions and resistances from in-plane and out-of-plane directions to be obtained. The measurement results were then input and analyzed with a model based on a transformation method developed by Montgomery, and thus the in-plane and out-of-plane conductivities could be detangled and derived. We also investigated how the conductivity anisotropy depends on the microstructure of the cellulose template onto which the conductive polymer self-organizes. We show that there is a relatively small difference between the in-plane and out-of-plane conductivities which is attributed to the unique 3D-structure of the composites. This new knowledge gives a better understanding of the possibilities and limitations for using the material in electronic and electrochemical devices. Graphical abstract Image 1 Highlights • Developed a simple to use generic tool for measuring 3-D resistances of thick conducting self-standing films. • The in-plane and out-of-plane conductivities were deduced by a method developed by Montgomery. • Both CNF-PEDOT:PSS and pulp-PEDOT:PSS films exhibit anisotropic conductivity. • CNF-PEDOT:PSS films show thickness independent anisotropic conductivity. • Pulp-PEDOT:PSS became less anisotropic with increasing thicknesses. [ABSTRACT FROM AUTHOR]

The reduction of dark current is required to enhance the signal-to-noise ratio and decrease the power consumption in photodetectors. This is typically achieved by introducing additional functional layers to suppress carrier injection, a task that proves to be challenging especially in printed devices. Here we report on the successful reduction of dark current below 100 nA cm −2 (at −1 V bias) in an inkjet printed photodetector by the insertion of an electron blocking layer based on poly[3-(3,5-di-tert-butyl-4-methoxyphenyl)-thiophene], while preserving a high quantum yield. Furthermore, the electron blocking layer strongly increases the surface energy of the hydrophobic photoactive layer, therefore simplifying the printing of transparent top electrodes from water based formulations without the addition of surfactants. [ABSTRACT FROM AUTHOR]