Organic photovoltaic (OPV) devices consist of multiple discrete layers, including organic films with complex and poorly-understood morphology. A key challenge in these systems is to understand the interfacial phenomena, which are known to strongly affect device performance. Traditional experimental techniques alone have proven insufficient for a detailed understanding of the role of interfaces in these devices. Here, we have used molecular dynamics simulations to investigate the influence of the electron-blocking layer, poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS), on the morphology of the active layer, poly(3-hexylthiophene):phenyl-C61-butyric acid methyl ester (P3HT:PCBM). Three different models of PSS:PEDOT were constructed representing different experimentally observed regions of the PSS:PEDOT surface. Similarly, two different models of P3HT:PCBM were constructed representing two typical weight ratios. Simulation results of P3HT:PCBM in close proximity to the PEDOT:PSS surface showed preferential PCBM deposition on the PEDOT surface, with the PCBM side chain showing affinity for the PEDOT:PSS surface. At the PEDOT:PSS surface, PCBM mainly binds with PEDOT transversely to complement the charge distribution of the PCBM side chain with surface PEDOT molecules. Our simulations have shown for the first time that the PCBM side chains are the driving force of PCBM deposition onto the PEDOT:PSS surface. These results have strong implications for both better understanding morphology development in OPV devices as well as for designing optimized interfaces to enable enhanced device performance.

Molecular simulations of interfacial interactions between electron-blocking and active layers in organic photovoltaic devices

248th National Meeting (2014)

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