Ultralow-work-function lithium oxide (LiO_x) as electron-selective contact for silicon heterojunction solar cell

Area of Science:

• Materials Science
• Renewable Energy
• Semiconductor Physics

Background:

• Dopant-free silicon solar cells offer cost-effective and simplified fabrication pathways.
• Electron-selective contacts are crucial for efficient charge extraction in solar devices.
• Lithium Oxide (LiOx) is explored as a novel material for enhancing solar cell performance.

Purpose of the Study:

• To investigate the potential of LiOx as an electron-selective contact in dopant-free silicon solar cells.
• To optimize the solar cell structure using LiOx and amorphous silicon layers for improved efficiency.
• To achieve high open-circuit voltage (Voc) and fill factor (FF) for enhanced power conversion efficiency (PCE).

Main Methods:

• Fabrication of a silicon solar cell with a full rear contact structure utilizing LiOx/Ag.
• Integration of an intrinsic hydrogenated amorphous silicon (i-a-Si:H) layer for surface passivation.
• Inclusion of a phosphorus-doped amorphous silicon (n-a-Si:H) layer as a transition layer between silicon and the contact.

Main Results:

• The LiOx/Ag contact demonstrated a low work function (2.39 eV) and low contact resistivity (7.2 mΩ cm²).
• Initial solar cell configuration with LiOx/Ag achieved Voc of 596 mV and FF of 80.4%.
• The optimized structure with i-a-Si:H and n-a-Si:H layers resulted in a Voc of 715 mV, FF of 78.10%, and a PCE of 20.62%.

Conclusions:

• LiOx is a promising electron-selective contact material for high-performance dopant-free silicon solar cells.
• Surface passivation and transition layers are effective strategies for further enhancing solar cell performance.
• The developed solar cell architecture demonstrates significant potential for low-cost, high-efficiency solar energy conversion.