Abstract
Inverted organic solar cells which required no electron selective layer were fabricated and their power conversion efficiency was found to improve irreversibly from 1.46% to 4.10% with post-processing light soaking for 2 hours. X-Ray photoelectron spectroscopy characterization revealed further segregation in surface composition at the interface and was found to explain the current density-voltage measurements. In addition, the light soaked devices were found to exhibit extended lifetime as compared to conventional devices. Since no electron selective layer was required, light soaking may be considered as a cost-effective method to achieve efficient inverted organic solar cells. © The Royal Society of Chemistry.