Investigation of AZO as an Alternative to ITO for Cathode Material in Organic Solar Cells

Abstract

AbstractA critical part of thin-film solar cells is conduction through the transparent electrode. Currently, the material of choice for the window electrode is Indium Tin Oxide (ITO). However, there is a huge scarcity of indium and also high processing cost is involved in ITO. Zinc based oxides are amazingly alluring alternative materials for ITO because of the colossal characteristic plenitude and low toxic quality of Zn. ZnO can be made conductive by doping with heteroatoms or by presenting oxygen opportunities. The best dopants are Al, Ga and F. In this work we have deposited nanostructured Al-doped ZnO (AZO) as a transparent window on polyethylene terephthalate (PET) substrate through sputtering. AZO thin films have been successfully deposited on PET as well as on glass substrate (1 in. × 1 in.) by sputtering (Mereu et al. in Physica Status Solidi (c) 11(9–10):1464–1467 , [1]; Wang et al. in Vacuum 89:127–131, [2]). AZO films on PET exhibited a marked decrease in resistance with an increase in thickness. Thickness measurement of AZO films deposited on flexible PET was done by Dektak Profilometer which gave the thickness of AZO to be 270 nm, 380 nm, 455 nm and 500 nm for 45 min, 60 min, 90 min and 135 min of sputtering time respectively. On the glass substrate resistivity ~ 30 0hms/sq has been achieved for AZO. Polyaniline a p-type polymer has been successfully deposited on AZO film on the glass. Replacing ITO by aluminum-doped ZnO (AZO) as a cathode material will substantially reduce the cost of organic solar cells (OSC) (AbdulAlmohsin et al. in J Arkansas Acad Sci 66:26–30, [3,4,]; Beek et al. in J. Mater. Chem. 15:2985–2988, [4]; Wang et al. in J. Mater. Chem. 20:862–866, [5]).