CuInS₂/PEDOT Photovoltaic Structure

Abstract

Structures based on combination of electrically conductive polymers with inorganic semiconductors are currently intensively investigated with the aim to prepare low-cost, largearea and flexible photovoltaic devices. In this study, multilayer structures consisting of CuInS₂ (CIS) and poly(3,4-ethylenedioxythiophene) (PEDOT) doped with polystyrenesulfonate (PSS) thin films were prepared and investigated for photovoltaic applications. Polycrystalline CIS absorber layers were synthesized on top of a layered structure on Cu tape substrate using socalled non-vacuum CISCuT technique. Thin PEDOT buffer layers doped with PSS were deposited onto KCN etched and vacuum annealed CIS films. The deposition was performed using the spin-casting technique from an aqueous dispersion of PEDOT/PSS mixed with Nmethylpyrrolidone, isopropanol, glycerin and epoxysilane additives. Optimal deposition parameters for stable PEDOT films with a good adherence to the surface of CIS were selected experimentally. The morphology and thickness of prepared films and structures was determined using SEM technique. Average film thickness was about of 1.5 μm for CIS and 50 nm for PEDOT films. Current-voltage and impedance characteristics were measured. Significant photovoltage and photocurrent of the photovoltaic structures were observed under standard illumination intensity. The best structure showed an open-circuit voltage of 510 mV and a shortcircuit current density of 20.2 mA/cm₂.