Optical Index Matching, Flexible Electrospun Substrates for Seamless Organic Photocapacitive Sensors

Abstract

Recent advances in optoelectronics are often based on thin‐film organic semiconductors. Interesting organic semiconductors are given by squaraines, small molecules that show excitonic coupling with visible light and are thus suitable for applications in solar cells and light sensors. While such squaraine thin films have already been proven to be suitable for stimulation of neuronal model cells, the integration into, e.g., the human eye to support blind people necessitates forming thin layers on seamless substrates. Herein, squaraine films are spin‐coated on electrospun nanofiber mats and nanomembranes, prepared from polyacrylonitrile, and made conductive by spin coating with poly(3,4‐ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS). The fibrous non‐woven texture of the nanofiber mats and membranes alters the thin film formation of the squaraine compound considerably compared with preparation on planar, nonsoaking substrates such as glass and polyethylene terephthalate (PET) foil demanding further engineering regarding material's choice and processing conditions.

Electrospinning for the Modification of 3D Objects for the Potential Use in Tissue Engineering

“…Only the conductive filament "Conductive PLA" (Figure 6d) shows a clear fiber orientation. It should be mentioned that the optical properties of such PAN nanofiber mats, independent of the fiber orientation, generally show a total transmission around 40-70% (depending on the nanofiber mat thickness) and a specular transmission near 0% throughout the whole visible spectrum without any maxima or minima, corresponding to the typical white color of such nanofiber mats [31,32]. Since CLSM images can only show the fiber near the sample surface and do not allow the depiction of the thickness of the nanofiber mat, the same samples are depicted by macroscopic photographs in Figure 7.…”

Optical Properties of Electrospun Nanofiber Mats

“…This is probably due to the high impact of scattering in nanofiber mats, usually causing a low transparency [95]. Transparency is thus often significantly increased if the nanofiber mat is in a wet state, with water or other fluids filling the voids inside [96], or if nanomembranes with low fiber content are prepared by electrospinning instead of fully fibrous membranes [97]. In some cases, such as in the light scattering layers of dye-sensitized solar cells (DSSCs), this fact is even advantageous [98,99].…”