Improving the Performance of Passivated Contact Crystalline Silicon Solar Cells with $\text{NiO}_{\mathrm{x}} / \text{MoO}_{\mathrm{x}}$ as a Composite Hole Transport Layer Using a Novel Annealing

In crystalline silicon (c-Si) solar cells, the design of effective carrier-selective contacts is a prerequisite for efficient $c$-Si solar cells. Wide bandgap transition metal oxides (TMOs) have low parasitic absorption compared to doped silicon films, but their carrier selectivity and passivation are not as good, so the solar cell efficiency is mediocre. Here, we employ $\text{NiO}_{\mathrm{x}} / \text{MoO}_{\mathrm{x}}$ composite film as an efficient hole-selective contact in $c$-Si solar cells. Interfacial carrier complexation is suppressed by inserting a silicon oxide ($\text{SiO}_{\mathrm{x}}$) tunneling layer on the c -Si surface, and carrier complexation is further reduced to improve the passivation of $c-\text{Si}$ cells by annealing in forming gas (FGA). And the deposition of $\text{MoO}_{\mathrm{x}}$ on the surface of $c-\text{Si}$ followed by the deposition of $\text{NiO}_{\mathrm{x}}$ alters the upward energy band bending of $c$-Si, which produces a band alignment that favors hole selectivity. Finally, we achieved a power conversion efficiency (PCE) of $\text{2 1. 6 6 \%}$ (fill factor (FF) 84.28 %) using $p-\text{Si} / \text{SiO}_{\mathrm{x}}(\text{FGA}) / \text{MoO}_{\mathrm{x}} / \text{NiO}_{\mathrm{x}} / \text{Ag}$ back-contact $c-\text{Si}$ solar cells. This study demonstrates an effective method to improve the performance of undoped $c$-Si solar cells using $\text{SiO}_{\mathrm{x}}(\text{FGA})$ as a passivation tunneling layer and $\text{NiO}_{\mathrm{x}} / \text{MoO}_{\mathrm{x}}$ as a composite hole transport layer (HTL).