Systematically varied annealing, encapsulation, and solvent vapor treatments are conducted to produce stable OPV devices with controlled film morphology and high performance when produced in air. Active layer films are analyzed by AFM, nanomechanical mapping, UV-Vis spectroscopy, and XRD. Devices prepared with isopropanol solvent vapor annealing combined with thermal annealing show the highest environmental resistance and performance. Such devices yield average PCE of 3.3 %, with stability to atmospheric exposure of up to 60 minutes prior to encapsulation. Encapsulated devices exposed to the laboratory environment for 30 days exhibit a decrease in PCE of approximately 15%. On application of a second thermal annealing step PCE is recovered to over 90% of the original value. The unprecedented air stability of the cells is attributed to the formation of an active layer with a stable, favorable morphology during the solvent vapor annealing process, which is associated with lower oxygen content films.

Journal of Polymer Science, Part B: Polymer Physics (2014), 52(23), 1511-1520. (Cover Article) DOI: 10.1002/polb.23605