Solution processed cathode and interconnecting layer of silver nanowires in an efficient inverted tandem organic solar cells

Abstract

Due to the potential of achieving high conductivity and high transparency, low-cost, large-area and flexibility for versatile applications as organic solar cells, silver nanowires (AgNWs) have attracted great attention as a good alternative to conventional ITO. However, design and production of conducting transparent film and interconnecting layers plays a very important role to achieve a high device performance. We discuss the benefit of the AgNWs inserted in the organic tandem solar cell devices as transparent electrode (TE) and as interconnecting layer (ICL) between the two subcells having actives layers with complementary absorption and made of poly(3-hexylthiophene):indene-C60 bisadduct and polythieno [3,4-b]thiophene/benzodithiophene: phenyl-C71-butyric acid methyl ester. ZnO nanoparticles have been used as interfacial layer in the ICL and lead to a decrease of the AgNWs roughness. The tandem cells on AgNWs show a good efficiency (PCE=9.23%), a short circuit current density of 11.23mA/cm2 close to the lower short circuit current of the two solar subcells, and an open circuit voltage (Voc=1.47V) matching the sum of the two subcells Voc. This suggests that the ICL provides a good carrier injection through the interfacial layer and an efficient recombination of the current coming from each subcells. Moreover, optical modeling is done in order to calculate the optimized active layers thicknesses and short term stability in open air evaluated.