Nano-imprint technique has been investigated as a method for producing optimized morphologies in organic photovoltaics (OPVs) with ordered heterojunction (OHJ). However, the interfacial morphology and the molecular aggregation states of OHJ-OPVs are still unclear. In this study, we evaluated the morphology of OHJ-OPVs by X-ray structure analyses.A line/space pattern was fabricated on of the P3HT thin film surface by nano-imprinting techniques, and then PCBM thin layer was deposited on the surface patterned P3HT thin film. The interfacial morphology and molecular aggregation state of the OHJ-OPVs were evaluated by AFM, SAXS and GIXD. SAXS and GIXD were carried out at BL03XU beam line of SPring-8.The nanostructure of the P3HT thin film surface could be observed by AFM, while it was 'buried' after the depositing of PCBM thin layer. In contrast, a clear scattering pattern was obtained from the 'buried' structure using SAXS. It was revealed that the interface get parabolic shape, which is represented by Gaussian distribution function, due to the partial phase mixing of P3HT and PCBM. Figure 1 illustrates the molecular aggregation state of OHJ-OPVs estimated by GIXD. The GIXD profiles revealed that the presence of vertically oriented P3HT chains in the nano-imprinted P3HT thin film, and also the face-on chain orientation is not present in prepared thin films. These nano-imprint induced morphologies exactly contribute to the power conversion efficiency improvement of the OHJ-OPVs.

Precise characterization of molecular aggregation state and interfacial structure in ordered heterojunction poly(3-hexylthiophene)-based photovoltaics

247th National Meeting (2014)

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