<br/>Many efforts have been made in the processing of organic photovoltaic devices to increase performance, including thermal annealing and solvent vapor annealing, wherein a photovoltaic active layer film is exposed to a solvent vapor-saturated atmosphere. Solvent vapor annealing was used in order to manipulate the morphology and performance of P3HT:PCBM polymer organic photovoltaic (OPV) devices. OPV active layers were annealed with a good solvent (dichlorobenzene), no solvent (air), or a poor solvent (isopropanol). Devices annealed with isopropanol vapors exhibited a higher hole mobility than the air control devices, which showed higher hole mobility than air- or dichlorobenzene-annealed devices, as calculated from dark-current measurements and fitting using the Mott-Gurney square law. These changes in performance are attributed to the changes in nanomorphology effected by solvent vapor annealing. Morphologies of films annealed solely with solvent vapor annealing, and in tandem with thermal annealing, were studied with UV-Vis spectroscopy, atomic force microscopy (AFM), and grazing incidence wide-angle x-ray scattering (GIWAXS). AFM analysis shows phase-separated domains on the order of exciton diffusion lengthscales. Coherence lengths of crystalline P3HT lamellae were determined by Scherrer analysis of the GIWAXS patterns, and followed the trend of DCB &lt; air &lt; IPA.

Effect of solvent vapor annealing on crystallinity and hole mobility in P3HT:PCBM polymer photovoltaics

253rd National Meeting (2017)

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