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This article presents a comprehensive study regarding the impact of the Al electrode on the surface passivation of three TiOx‐based passivating selective contacts: TiOx:Al/LiFx/Al,TiOx/LiFx/Al, and a‐Si/TiOx:Al/LiFx/Al. A deterioration in passivation is recorded after the deposition of the Al electrode at close to room temperature, where the deterioration correlated to the Al thickness. A thin Al (10 nm) electrode resulted in the most severe passivation decline, while samples with a 100 nm Al electrode showed much less passivation deterioration. Furthermore, it is found that a low‐temperature annealing step led to a partial recovery of the passivation, particularly in the case of TiOx:Al/LiFx/Al and a‐Si/TiOx:Al/LiFx/Al contacts. The presented discovery in this article provides crucial insight into the importance of characterization and evaluation of passivating contacts, which is demonstrated here to be highly sensitive to the deposited metal thickness and the interfacial layers, as well as to the post‐deposition annealing. [ABSTRACT FROM AUTHOR]

Tunnel silicon oxides form a critical component for passivated contacts for silicon solar cells. They need to be sufficiently thin to allow carriers to tunnel through and to be uniform both in thickness and stoichiometry across the silicon wafer surface, to ensure uniform and low recombination velocities if high conversion efficiencies are to be achieved. This paper reports on the formation of ultra-thin silicon oxide layers by field-induced anodisation (FIA), a process that ensures uniform oxide thickness by passing the anodisation current perpendicularly through the wafer to the silicon surface that is anodised. Spectroscopical analyses show that the FIA oxides contain a lower fraction of Si-rich sub-oxides compared to wet-chemical oxides, resulting in lower recombination velocities at the silicon and oxide interface. This property along with its low temperature formation highlights the potential for FIA to be used to form low-cost tunnel oxide layers for passivated contacts of silicon solar cells. [ABSTRACT FROM AUTHOR]

Sub-stoichiometric molybdenum oxide (MoO x ) films are commonly deposited on crystalline silicon (c-Si) solar cells by thermal evaporation, a process that requires high vacuum and provides limited control of oxide stoichiometry and in consequence limited control of hole transport properties. Here, we report on a method of forming MoO x films on crystalline silicon wafer surfaces by spin-coating hydrogen molybdenum bronze solutions. It is shown that a ∼2.8 nm thick interfacial SiO x layer forms under the spin-coated MoO x films and that the as-deposited MoO x is amorphous and sub-stoichiometric ( x = 2.73), with the concentration of oxygen vacancies in the MoO x being able to be reduced by annealing in air. The as-deposited MoO x films show comparable contact resistivity and passivation quality on c-Si wafers to thermally-evaporated MoO x , demonstrating their potential to be an effective hole-selective contact layer for c-Si solar cells and an alternative for thermally-evaporated films. [ABSTRACT FROM AUTHOR]

Wet chemical anodic oxides may represent an alternative way of forming passivating dielectric layers for silicon solar cells. In this paper we describe the requirements to achieve anodisation using a field-induced process which involves forward-biasing a p-n junction to make an n-type silicon wafer surface anodic. Although potentially very large currents can be achieved using this method, it is shown that the anodisation current is practically limited by the resistances in the electrochemical circuit. Furthermore, depletion regions can form at both surfaces when the wafer is under forward-bias. This can be addressed by either ensuring that the surfaces are sufficiently-doped for ohmic contact or by using light to generate a photocurrent in the depletion regions of the wafer. [ABSTRACT FROM AUTHOR]