Interfacial Modification of the Electron Collecting Layer of Low-Temperature Solution-Processed Organometallic Halide Photovoltaic Cells Using an Amorphous Perylenediimide
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The efficiency of organometallic halide photovoltaic cells can be improved by interfacial modification of the titanium oxide (TiOx) electron collecting layer by a thin layer of an organic material. Enhancements of power conversion efficiency up to 37% were obtained with PC61BM, but the performance is highly dependent on processing conditions and PCBM is still an expensive material. Herein, a glass-forming perylenetetracarboxylicdiimide derivative (PDI-glass) was used as interface material. The devices were optimized with varying PDIglass thickness. With an optimal 10 nm-thickness, a power conversion efficiency increase of 39% were obtained, with an increase in short-circuit current from 9.7 to 11.05 mA cm−2 and fill factor from 0.51 to 0.61. Aside from the thickness of the PDI-glass layer, the process yields consistent results independent of the processing conditions. Photoluminescence spectra revealed the presence of charge transfer at the PDI-glass – active layer interface. The films were further studied by X-ray diffraction (XRD), atomic force microscopy (AFM), and scanning electron microscopy (SEM).