Wide-Bandgap Binary Metal Oxide Electron Transport Layer for Solar Cells

Area of Science:

• Materials Science
• Photovoltaics
• Semiconductor Devices

Background:

• Metal oxides are explored as alternatives to doped silicon in solar cells to reduce light absorption and manufacturing complexity.
• Current metal oxide materials face limitations in conductivity and long-term stability, hindering device performance.

Purpose of the Study:

• To introduce atomic layer deposition (ALD) zinc tin oxide (ZTO) as a novel electron-selective material for crystalline silicon (c-Si) solar cells.
• To investigate the electrical and optical properties of ZTO thin films and their impact on solar cell performance and stability.

Main Methods:

• Fabrication of ZTO thin films using atomic layer deposition (ALD).
• Characterization of ZTO film properties, including optical bandgap, transmission, work function, and oxygen vacancy concentration.
• Fabrication and testing of c-Si solar cells incorporating ZTO as an electron-selective layer, with and without a lithium fluoride (LiF) interlayer.
• Evaluation of device performance (PCE) and long-term operational stability.

Main Results:

• ZTO thin films exhibit an expanded optical bandgap and high transmission.
• The c-Si/ZTO/Al structure demonstrates ohmic contact characteristics due to ZTO's properties.
• Insertion of LiF reduces contact resistivity to 2.09 mΩ·cm².
• A c-Si solar cell with SiO_x/ZTO/LiF/Al achieved a power conversion efficiency (PCE) of 22.5% and maintained stability for over 1000 hours in air.

Conclusions:

• ZTO/LiF/Al is a promising electron transport layer for c-Si solar cells, offering improved efficiency and stability.
• ZTO thin films show potential for applications beyond c-Si solar cells, including perovskite and organic solar cells.