Enhancement of NiO_x/Poly‐Si Contact Performance by Insertion of an Ultrathin Metallic Ni Interlayer

Nickel oxide () is a promising hole transport material for perovskite/Si tandem solar cells. Various silicon cell architectures may be used as bottom cells. The polycrystalline (poly‐Si) tunnel diode is expected to be a high‐efficiency interconnection scheme between the two subcells of monolithic tandems in p‐i‐n configuration with a high thermal budget, excellent passivation properties, and low contact resistivity. However, is then interfaced to poly‐Si() and the chemical integrity of the interface due to the necessity of annealing treatments has to be questioned. For this purpose, the /poly‐Si contact resistivity for different annealing temperatures is investigated between 100 and 500 °C, and two different deposition techniques, namely, wet‐chemically applied and sputter‐deposited . The values of more than are obtained. The insertion of a nm‐thin metallic Ni interlayer is shown to enable a tremendous decrease of the contact resistivity by 2–3 orders of magnitude. The formation of is proven by highly resolved (scanning) transmission electron microscopy ((S)TEM) coupled with energy‐dispersive X‐ray spectroscopy (EDXS). This interfacial engineering approach is expected to provide an effective way of improving the contact properties and integrability of into various tandem cell processes.