Enhancement of NiOx/Poly-Si Contact Performance by Insertion of an Ultrathin Metallic Ni Interlayer

Nickel oxide ((Formula presented.)) 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) (Formula presented.) 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, (Formula presented.) is then interfaced to poly-Si((Formula presented.)) and the chemical integrity of the interface due to the necessity of annealing treatments has to be questioned. For this purpose, the (Formula presented.) /poly-Si contact resistivity for different annealing temperatures is investigated between 100 and 500 °C, and two different (Formula presented.) deposition techniques, namely, wet-chemically applied and sputter-deposited (Formula presented.). The values of more than (Formula presented.) 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 (Formula presented.) 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 (Formula presented.) into various tandem cell processes.