Influence of organic active layer morphology on plasmonic light-trapping

Here, we show that the morphology of organic bulk-heterojuction (BJH) thin films strongly influences whether plasmonic modes supported by an electrode are absorbed or outcoupled (leaked) from the organic thin films. Using optical dark-field scattering, full-field electromagnetic modelling and grazing-incidence, wide-angle X-ray scattering, we find that more crystalline organic active layers, such as P3HT:PCBM trap surface plasmons while more amorphous organic thin films such as PTB7:PC₇₀BM and PCDTBT:PC₇₀BM facilitate leakage of surface plasmon polaritons. This is an important finding because it indicates that plasmonic light trapping can be improved in thin-film organic active layers using more crystalline active layers.