Investigation of metal-nickel oxide contacts used for perovskite solar cell

Perovskite solar cells (PSCs) have been able to raise new hopes for a revolution in solar cell technology. However, there are many challenges which need to be resolved in order to reveal the true potential of this technology. An issue which should be addressed in designing PSCs is the metal-hole transporting material (HTM) contact’s property. One of the most promising inorganic HTMs for PSCs is Nickel oxide. Although NiO has been extensively studied in the literature, to the best of our knowledge metal-NiO junctions have never been studied experimentally. In this work, metal-NiO contacts have been investigated to indicate a novel route to choose proper metals in designing PSCs based on NiO as the HTM. Thus, NiO layers with four various metals have been fabricated and comprehensively explored. The contacts have been characterized using the transmission line method (TLM), and a contact resistivity ranging from about 2052 to 34 mΩ⋅cm2 was observed. I-V characteristics showed ohmic behavior in all metal-NiO cases. These results indicate that Fermi level pinning occurs at the valence band edge of the NiO. Further discussions resulted in suggesting Nickel as the most applicable candidate on NiO have been also included.