Analysis of Charge Transport and Conduction Mechanisms in Metal Porphyrin/PEDOT:PSS Films Used in Light-Sensing Applications

This work proposes the study of light-sensitive resistive sensors composed of dispersed heterojunctions (BHJs) in a poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) matrix, fabricated from cobalt and palladium porphyrins (CoOEP and PdOEP), and mixed with ethylanthraquinone (EAQ). Topographical characterization was performed using atomic force microscopy. In addition, the BHJs were characterized by their transmittance and fluorescence, and their band gap of 3.6 eV was similar for both heterojunctions and independent of the metal in the porphyrin. However, transmittance and fluorescence are more strongly correlated with the metal of the macrocycle. With PdOEP-EAQ/PEDOT:PSS and CoOEP-EAQ/PEDOT:PSS films as active layers, sensitive resistive sensors were fabricated and optimized by embedding SnO2 and ZnO nanoparticles in PEDOT:PSS, as well as aluminum hydroxyquinoline, within the same polymer matrix. The devices fabricated on Tetra Pak and glass substrates were electrically characterized over a voltage range of −1.1 to 1.1 V under both white illumination and darkness. The results show that glass devices deposited with SnO2-PEDOT:PSS and ZnO-PEDOT:PSS exhibit improved linearity of electrical conduction under dark conditions. Furthermore, for the SnO2-PEDOT:PSS/CoOEP-EAQ device, the electron mobility and free carrier density were estimated, yielding values of <!-- MathType@Translator@5@5@MathML2 (no namespace).tdl@MathML 2.0 (no namespace)@ -->