Effect of Al Electrodes on Surface Passivation of TiO_x Selective Heterocontacts for Si Solar Cells

Abstract

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.

High‐performance perovskite/silicon heterojunction solar cells enabled by industrially compatible postannealing

“…When Al capping layer is considered, PCD method becomes unsuitable to characterize the τ eff . Recently, Liang also found that fully metalized samples are not allowed the minority carrier lifetime to be measured with the PCD technique 44 . Therefore, here we characterize τ eff in the final device level by Suns‐ V OC measurement mode 45 .…”

“…Recently, Liang also found that fully metalized samples are not allowed the minority carrier lifetime to be measured with the PCD technique. 44 Therefore, here we characterize τ eff in the final device level by Suns-V OC measurement mode. 45 Note that in this method, the τ eff does not only include the carrier recombination within the Si wafer and the electron-selective layer but also include the recombination beneath the front electrodes, hole-selective layer, and the Al capping layer.…”

Optimization of a Solution-Processed TiOx/(n)c-Si Electron-Selective Interface by Pre- and Postdeposition Treatments

“…Second, it must be noted that all of the passivation parameters reported in Table are for prior metallization. It has been demonstrated that the adverse influence of metallization (Al) on the passivation quality is a common concern for all TiO x -based contacts, which imposes a reduced V oc compared with i V oc at the cell level. − …”

High-performance perovskite/silicon heterojunction solar cells enabled by industrially compatible post annealing

“…Recently, Liang also found that fully metalized samples are not allowed the minority carrier lifetime to be measured with the PCD technique. 43 Therefore, here we characterizeτ eff in final device level by Suns-V oc measurement mode. 44 Figure 2c shows that theτ eff increases with post-annealing temperature (within 300 °C), again demonstrating that the passivation effect is improved by post-annealing treatment.…”