Study of Dactylopius opuntiae and its electrical properties as thin film for application in organic devices

Abstract In this work, we perform morphological and physicochemical studies of Dactylopius opuntiae (cochineal) with electron microscopy and explore their use as a transporting layer for organic electronic devices. The charge transport properties of this pigment were investigated through current-voltage measurements. The current-voltage characteristics have shown that the cochineal can be used as a hole-transporting layer (HTL) with mobility of 5.30 ± 0.03 × 10−4cm2V−1 s−1. Different analyses were realized on this pigment and the results were compared with other HTL organic compounds, as Poly(3,4-ethylene dioxy thiophene): poly(styrene sulfonate) (PEDOT:PSS). The results show that the cochineal pigment does not produce luminescence and has a band gap of 2.6 ± 0.2 eV with optical absorption in the visible range. The roughness of cochineal thin films was measured after filtering the solution with a value of 11.8 ± 0.2 nm. Cochineal and PEDOT:PSS were successfully used as HTL in the fabrication of a [Ir(fliq)2acac] based PHOLED. The results show an increase in the electroluminescent color purity emission due to the filtering action of the natural pigment when compared with the PEDOT:PSS based in this device.