Experimental and Theoretical Investigation of Photosensitive ITO/PEDOT:PSS/MEH-PPV/Al Detector

Abstract

One of widely investigated materials for photodiode, light-emitting device, and solar cell applications is a soluble conjugated polymer poly(2-methoxy-5- (2,9-ethyl-hexyloxy)-1,4-phenylene vinylene) or MEH-PPV. In this paper we present experimental results on MEH-PPV polymer and ITO/PEDOT:PSS/MEH-PPV/Al photodetector, where ITO and PEDOT:PSS stand for indium tin oxide and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate), respectively. Thin polymer films were fabricated by spin-coating technique. The characterization of the material and devices are done in air at room temperature. The experimental results include optical absorption of MEH-PPV and determination of the optical absorption coefficient, photocurrent dependence on optical power, light wavelength, bias voltage, and polymer thin film thickness. Theoretical modeling is based on drift-diffusion and continuity equations for hole polarons, as well as assumption that the charge carrier recombination process is bimolecular. The bimolecular recombination mechanism implies that the photocurrent depends on the square root of the optical power, which is confirmed with our experimental results.