Hole selective MoOx contact for silicon solar cells

Area of Science:

• Materials Science
• Solid-State Physics
• Renewable Energy Technologies

Background:

• Molybdenum oxide (MoOx) is typically viewed as a semiconductor with a 3.3 eV band gap.
• Developing efficient and cost-effective contacts for semiconductors is crucial for device performance.
• Current methods for creating contacts often involve complex doping processes.

Purpose of the Study:

• To investigate the potential of ultrathin molybdenum oxide (MoOx) as a hole-selective contact for n-type silicon.
• To demonstrate a room-temperature processed oxide/silicon solar cell.
• To explore the electronic properties of MoOx beyond its traditional semiconductor classification.

Main Methods:

• Fabrication of an ultrathin (∼15 nm) MoOx layer on n-type silicon.
• Characterization of the MoOx layer using X-ray photoelectron spectroscopy (XPS).
• Fabrication and efficiency testing of the resulting oxide/silicon solar cell.

Main Results:

• Achieved a power conversion efficiency of 14.3% for the room-temperature processed solar cell.
• XPS analysis revealed MoOx behaves as a high work function metal (∼6.6 eV) due to oxygen vacancies, not a typical semiconductor.
• Demonstrated the effectiveness of nm-thick transition metal oxides as dopant-free contacts for silicon.

Conclusions:

• Ultrathin MoOx serves as an effective transparent hole-selective contact for silicon.
• This approach enables efficient, room-temperature processed solar cells without doping.
• The findings open avenues for novel junctionless devices, including solar cells, LEDs, photodetectors, and transistors.