Interfacial modification of the electron collecting layer of low-temperature solution-processed organometallic halide photovoltaic cells using an amorphous perylenediimide

•A glass-forming perylenediimide derivative was used as an interfacial layer in perovskite-based photovoltaic cells with solution-processed TiOx as electron transport layer.•Efficiency enhancements up to 39% were obtained at an optimal thickness of 10 nm.•The addition of this interfacial layer leads to larger perovskite nanostructure formation.•Charge transfer between the perovskite and interfacial layers was improved.

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 PDI-glass 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).

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