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

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.