A BHJ-thin-film/liquid-electrolyte based electrochemical-sensor for visible light-detection

Abstract

The current study presents a new type of inexpensive and very sensitive bulk heterojunction (BHJ) organic photo-sensor (OPS) configuration that incorporates a layer of liquid electrolyte into the conventional BHJ photodiode arrangement. Initially, a P3HT:PCBM blend based photo-anode was deposited onto ITO substrates using spin coating. Then the semiconductor coated photo-anode was attached to a Pt/ITO counter electrode. A 40 µm gap between photo-anode and counter electrode was filled with a liquid (iodine based) HI-30 electrolyte. Various electrical parameters including ideality factor, series and shunt resistance were extracted from the current–voltage characteristics under dark and light conditions. The value of mobility measured under dark conditions was found to be 25.58 × 10⁻⁶ m² V⁻¹ s⁻¹. In addition, the samples were found to have a series and shunt resistance of 133.33 Ω and 74.70 kΩ, respectively. Under illumination, the fabricated photodiodes exhibited a linear current–irradiance relationship, with a rapid response time, when exposed to transient light, thus making the newly proposed hybrid BHJ photo-diode configuration a potential alternative to the conventional photo-sensors.