Solvent extraction induced nano-porous zinc oxide as an electron transport layer for inverted polymer solar cells

A facile and cost-effective method is demonstrated to prepare a nano-porous rugged zinc oxide (ZnO) film without complicated processes and strict condition. A sol-gel derived ZnO is simply coated onto the substrate and subsequently removed the unreacted precursor and residual matters by solvent extraction. Thus, the precursor and residuals provide the vacancy to form a highly rugged surface. Compared with the flat ZnO film, the rugged ZnO is not only performs better purity than the flat film, but also increases the interfacial contact between the ZnO and bulk-heterojunction layer. By using the rugged ZnO as an electron transport layer, an enhancement of 20% in photocurrent generation could be achieved in an inverted poly(3-hexylthiophene):[ 6,6]-phenyl C-61 butyric acid methyl ester solar cell together with highly air stability. (C) 2012 Elsevier B.V. All rights reserved.