Low-temperature fabrication of sol-gel NiO film for optoelectronic devices based on the 'fuel' of urea

In this work, NiO coating is fabricated by a low temperature 'combustion process' driven by 'chemical oven' on quartz and indium tin oxide (ITO) substrates followed by an annealing process in air at 225 °C for 2 h. The NiO coating is analyzed by means of thermalgravimetric differential thermal analysis (TG-DTA), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electric microscopy (SEM), atomic force microscope (AFM), and UV-visible spectrometer. A prelimilary photovoltaic performance measurement of the fabricated device (ITO/NiO/poly-TPD/PC71BM/Al) shows a short circuit current density (Jsc) of 5.28 mA cm−2 and power conversion efficiency (PCE) of 1.56% under an illumination of 100 mW cm−2. The PCE of device with combustion NiO HTLs is almost 10-fold higher than those of the devices based on common NiO HTLs. The combustion fabricated NiO coating may provide an effective approach to fabricate other NiO-based optoelectrical devices at relative low temperature.