Self-Assembled TiO2 Nanorods as Electron Extraction Layer for High-Performance Inverted Polymer Solar Cells

Abstract

We demonstrate the use of TiO2 nanorods with well-controlled lengths as excellent electron extraction materials for significantly improving the performance of inverted polymer solar cells. The cells containing long nanorods outperform the devices using amorphous TiO2 particles as the electron extraction layer, mainly by a 2-fold increase in short-circuit current and fill factor. The enhanced charge extraction is attributed to the high electron mobility in crystalline nanorods and their preferential alignment during film formation. Furthermore, transient photocurrent studies suggest the presence of fewer interfacial and internal defects in the nanorod interlayers, which can effectively decrease carrier recombination and suppress electron trapping.