Tailoring opto-electronic and interface properties via electrochemical doping in Poly(3-hexylthiophene)

Abstract

The thin films of electropolymerized poly(3-hexylthiophene) [e-P3HT] are simultaneously doped on the transparent indium tin oxide substrate via anodic oxidation. Distinctive doping levels are achieved by systematically de-doping the films in a reverse bias electrochemical process. Raman characterization shows the presence of doping-induced polarons. In the UV–Vis spectrum, two distinct absorption regions are found for P3HT suggesting the presence of doping-induced polarons and the Urbach calculations reveal a fine-tuning of bandgap with doping level. Further, the PL studies show exponential quenching in intensity due to charge transfer which can be precisely tuned by the doping level in the e-P3HT. The current-voltage measurements under the illumination of a 532 nm laser on a sandwich device with top contact of silver are also performed and it is found that an optimized doping level is essential to acquire the best photo response. Impedance spectroscopy on the devices and their equivalent circuit analysis reveals that in addition to the bulk system, doping can also vastly modify the interfacial properties. Our studies pave the direction to tailor and optimize different optoelectronic and interface-related properties of e-P3HT thin films via electrochemical doping for optimized optoelectronic devices and applied physics studies.