Hydrogenation Mechanisms of Poly‐Si/SiOx Passivating Contacts by Different Capping Layers. Issue 3 (26th November 2019)

• Record Type: Journal Article
• Authors: Truong, Thien N.; Yan, Di; Chen, Wenhao; Tebyetekerwa, Mike; Young, Matthew; Al-Jassim, Mowafak; Cuevas, Andres; Macdonald, Daniel; Nguyen, Hieu T.
• Is Part Of: Solar RRL. Volume 4:Issue 3(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2019-11-26
• Subjects: aluminum oxide -- doped polycrystalline silicon -- forming gas anneal -- hydrogenation -- passivating contacts -- silicon nitride; Solar energy -- Periodicals; Photovoltaic power generation -- Periodicals; Solar energy -- Research -- Periodicals; Photovoltaic power generation -- Research -- Periodicals; Periodicals; 333.7923
• DOI: 10.1002/solr.201900476
• Languages: English
• ISSNs: 2367-198X

Abstract

Abstract : Herein, posttreatment techniques of phosphorus‐doped poly‐Si/SiO x passivating contacts, including forming gas annealing (FGA), atomic layer deposition (ALD) of hydrogenated aluminum oxide (AlO x :H), and plasma‐enhanced chemical vapor deposition (PECVD) of hydrogenated silicon nitride (SiN x :H), are investigated and compared in terms of their application to silicon solar cells. A simple FGA posttreatment produces a significant increase in the implied open circuit voltage (iVoc ) and the effective minority‐carrier lifetime ( τ eff ) of high‐resistivity crystalline Si (c‐Si) samples, whereas low‐resistivity samples show a minimal change. Treatment by means of AlO x :H and/or SiN x :H followed by postdeposition FGA results in a universal increase in τ eff and iVoc for all substrate resistivities (as high as 12.5 ms and 728 mV for 100 Ω cm and 5.4 ms and 727 mV for 2 Ω cm n‐type c‐Si substrates). In addition, both the FGA and AlO x :H + FGA techniques can inject sufficient hydrogen into the samples to passivate defects at the SiO x /c‐Si and poly‐Si/SiO x interfaces. However, this hydrogen concentration is insufficient to neutralize both the nonradiative defects inside the poly‐Si films and dangling bonds associated with the amorphous Si phase present in them. The hydrogen injected by the SiN x :H + FGA technique can passivate both the interfaces and the defects and dangling bonds within the poly‐Si film. These results are confirmed by low‐temperature photoluminescence spectroscopy, Fourier transform infrared spectroscopy, and dynamic secondary‐ion mass spectrometry measurements. Abstract : One way to overcome the limitation of poly‐Si passivating contacts is to neutralize each defect inside the film with the addition of a hydrogen atom, that is, by performing a hydrogenation step. Although there are many effective methods to hydrogenate the poly‐Si layer, there are significant differences between them. Herein, the mechanisms of various hydrogenation techniques are reported.