Air processed P3HT:PCBM photovoltaic cells: Morphology correlation to annealing, degradation, and recovery

ABSTRACT 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 (SVA) combined with thermal annealing (TA) show the highest environmental resistance and performance. Such devices yield average PCE of 3.3%, with stability to atmospheric exposure of up to 60 min prior to encapsulation. Encapsulated devices exposed to the laboratory environment for 30 days exhibit a decrease in PCE of ∼15%. On application of a second TA 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 SVA process, which is associated with lower oxygen content films. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014, 52, 1511–1520 The necessity for an inert atmosphere during device fabrication is an obstacle to the commercialization of organic photovoltaics. In this study, isopropanol solvent vapor annealing in combination with encapsulation and thermal annealing (TA) yields devices with 3.3% power conversion efficiency, even after 1 h exposure to air. Cells aged for 30 days show performance recovery with a second TA step. The performance is related to morphology and oxygen absorption in the active layer.