Enhanced High-Temperature Long-Term Stability of Polymer Solar Cells with a Thermally Stable TiOx Interlayer

The short lifetime of polymer-based solar cells is an obstacle to their commercialization. Since solar cells would be operated at elevated temperature, it is necessary to improve their high-temperature long-term stability. Insertion of a TiOx interlayer between an Al electrode and the active layer could result in enhanced performance and long-term stability. However, the operational lifetime at elevated temperature becomes worse because of its significant morphological change during high-temperature operation, which possibly deteriorates the interface between Al and the active layer. In this paper, the role of a unique type of a TiOx interlayer from a newly designed polymeric precursor is presented. The operational lifetime at elevated temperature has been much improved by introducing such TiOx interlayer. It is attributed to an improved interfacial stability, owing to relatively reduced morphology change at high-temperature operation. The effectiveness of this unique feature makes it possible to fabricate more efficient organic solar cells by adopting a post-annealing process.