Eur. Phys. J. Appl. Phys. 44, 223-228 (2008)
https://doi.org/10.1051/epjap:2008166

On the improvement of the efficiency of organic photovoltaic cells by the presence of an ultra-thin metal layer at the interface organic/ITO

¹ Université de Nantes, Nantes Atlantique Universités, LAMP, EA 3825, Faculté des Sciences et des Techniques, 2 rue de la Houssinière, BP 92208, 44000 Nantes, France
² Université de Badji-Ammar Annaba, Faculté des Sciences, Algeria
³ Université de Lomé, Togo

Corresponding author: jean-christian.bernede@univ-nantes.fr

Received: 22 January 2008
Accepted: 22 August 2008
Published online: 24 October 2008

Abstract

Organic photovoltaic cells based on the multilayers structure, indium tin oxide (ITO)/copper-phthalocyanine(CuPc)/fullerene(C₆₀)/aluminium tris(8-hydroxyquinoline) (Alq₃)/aluminium, have been studied. When an ultra-thin metal layer is deposited onto the surface of the ITO anode the power conversion efficiency of the cells is significantly improved. The improvement depends on the ITO used. These differences have been attributed to the difficulty to control the surface chemistry of ITO. The best result has been obtained with a gold layer thick of about 0.5 nm. We propose that the gold ultra-thin film, which is too thin to be continuous, allows to improve the agreement between the work function of the anode and the highest occupied molecular orbital (HOMO) of the organic donor CuPc and to passivate the surface contamination of ITO.