Carrier transport through the ultrathin silicon-oxide layer in tunnel oxide passivated contact (TOPCon) c-Si solar cells

Zhang, Zhi; Zeng, Yuheng; Jiang, Chun-Sheng; Huang, Yuqing; Liao, Mingdun; Tong, Hui; Al-Jassim, Mowafak; Gao, Pingqi; Shou, Chunhui; Zhou, Xiaoling; Yan, Baojie; Ye, Jichun

doi:10.1016/j.solmat.2018.07.025

Carrier transport through the ultrathin silicon-oxide layer in tunnel oxide passivated contact (TOPCon) c-Si solar cells

Journal Article · Fri Aug 03 00:00:00 UTC 2018 · Solar Energy Materials and Solar Cells

DOI:https://doi.org/10.1016/j.solmat.2018.07.025· OSTI ID:1467556

Zhang, Zhi ^[1]; Zeng, Yuheng ^[2]; Jiang, Chun-Sheng ^[3]; Huang, Yuqing ^[4]; Liao, Mingdun ^[2]; Tong, Hui ^[2]; Al-Jassim, Mowafak ^[3]; ^[2]; Shou, Chunhui ^[5]; Zhou, Xiaoling ^[6]; Yan, Baojie ^[2]; Ye, Jichun ^[2]

Ningbo Materials Inst. of Technology and Engineering, Ningbo City (China); Kunming Univ. of Science and Technology (China)
Ningbo Materials Inst. of Technology and Engineering, Ningbo City (China)
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Ningbo Materials Inst. of Technology and Engineering, Ningbo City (China); Zhejiang Normal Univ., Jinhua (China)
Zhejiang Energy Group R&D (China)
Kunming Univ. of Science and Technology (China)

The carrier transport through the silicon-oxide (SiO_x) layer in tunnel oxide passivated contact (TOPCon) c-Si solar cells has been studied experimentally and by simulation. The current intensity versus voltage (J-V) characteristics of GaIn/n-c-Si/SiO_x/n⁺-poly-Si/Al structures shows a linear Ohmic characteristic, while a non-Ohmic behavior is observed in the samples without the n⁺-poly-Si contact layer. Conductive Atomic Force Microscopy (c-AFM) images reveal some current spikes on the surface of the samples, which could be related to the transport through pinholes. The simulation results show that 1) a rectification characteristic is obtained when only the tunneling mechanism is included, 2) both the reverse saturation current and the forward current increase when a small amount of transport through pinholes is introduced, and 3) finally a linear Ohmic behavior is observed when the pinhole transport component reaches a certain level. Furthermore, the simulation for whole TOPCon solar cells provides some useful results. For very thin SiO_x (< 1.2 nm), the tunneling provides sufficient high tunneling probability and high efficiency TOPCon solar cells can be obtained without transport through pinholes if the passivation is ensured; while for a relatively thick SiO_x (> 1.2 nm) without the transport through pinholes, the TOPCon solar cell shows a poor fill factor (FF) with a high series resistance (Rs) because the tunneling does not provide a sufficient high transport channel for carrier transport, and the introduction of a small number of transports through pinholes improves the FF and reduces the Rs, hence improves the PCE. However, a high possibility for carrier going through pinholes reduces all of the performance parameters and degrades PCE for all the cases simulated. Therefore, an optimized pinhole density and size distribution is critical engineering for solar cell performance optimization. However, the establishment of an optimized method to precisely control the pinhole formation and characterization is still on the way.

View Accepted Manuscript (DOE)

Research Organization:: National Renewable Energy Lab. (NREL), Golden, CO (United States)

Sponsoring Organization:: USDOE Office of Energy Efficiency and Renewable Energy (EERE)

Grant/Contract Number:: AC36-08GO28308

OSTI ID:: 1467556

Report Number(s):: NREL/JA--5K00-72260

Journal Information:: Solar Energy Materials and Solar Cells, Journal Name: Solar Energy Materials and Solar Cells Journal Issue: C Vol. 187; ISSN 0927-0248

Publisher:: ElsevierCopyright Statement

Country of Publication:: United States

Language:: English

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Improvement of Surface Passivation of Tunnel Oxide Passivated Contact Structure by Thermal Annealing in Mixture of Water Vapor and Nitrogen Environment Zhang, Zhi; Liao, Mingdun; Huang, Yuqing Solar RRL, Vol. 3, Issue 10 https://doi.org/10.1002/solr.201900105	journal	June 2019
Poly-Si/SiO _x /c-Si passivating contact with 738 mV implied open circuit voltage fabricated by hot-wire chemical vapor deposition Li, Shenghao; Pomaska, Manuel; Hoß, Jan Applied Physics Letters, Vol. 114, Issue 15 https://doi.org/10.1063/1.5089650	journal	April 2019

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Carrier transport through the ultrathin silicon-oxide layer in tunnel oxide passivated contact (TOPCon) c-Si solar cells

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