Enhanced high-temperature long-term stability of polymer solar cells with a thermally stable TiO_x 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 TiO_x 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 TiO_x interlayer from a newly designed polymeric precursor is presented. The operational lifetime at elevated temperature has been much improved by introducing such TiO_x 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.