Chad Snyder - Poly(3-hexylthiophene) and [6,6]-Phenyl‑C61-butyric Acid Methyl Ester Mixing in Organic Solar Cells

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      Publication Details (including relevant citation   information):

      H.W. Ro, B. Akgun, B.T. O’Connor, M. Hammond, R.J. Kline, C.R   Snyder, S.K. Satija, A.L. Ayzner, M.F. Toney, C.L. Soles and D.M.   DeLongchamp, Macromolecules 45,   6587-6599 (2012).


      The mixing behavior of the hole- and   electron-transportingmaterials in bulk heterojunction (BHJ)   organic photovoltaic (OPV) blends plays a key role in determining   the nanoscale morphology, which is believed to be a decisive   factor in determining device performance. We present a systematic   investigation of the mixing behavior between   poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid   methyl ester (PCBM) in model multilayer structures. The bilayer   structures are composed of amorphous PCBM that is mechanically   laminated to different P3HT layers with varying degrees of   crystallinity. We find that mixing is significantly decreased as   the crystallinity of P3HT is increased. The mixing behavior can   be explained as resulting from (1) nearly complete miscibility of   PCBM with amorphous P3HT (based on our results from regiorandom   P3HT) and (2) the existence of tie chains between crystalline   P3HT domains that restrain the swelling of the P3HT layer by   PCBM. We also introduce a unique PCBM−P3HT−PCBM trilayer   structure where one of the PCBM layers is highly crystalline. The   crystalline PCBM dramatically alters the mixing behavior. Initial   mixing of the amorphous PCBM into P3HT is followed by rapid cold   crystallization at the crystalline PCBM layer, which depletes the   PCBM in the P3HT layer. These bilayer and trilayer experiments   illustrate that mixing of P3HT and PCBM is influenced by multiple   factors, such as the semicrystalline nature of P3HT (overall   crystallinity, characteristics of amorphous chains) and phase   (amorphous or crystalline) of the PCBM.

      Christopher Soles

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