Atomic-Layer-Deposited TiO Nanolayers Function as Efficient Hole-Selective Passivating Contacts in Silicon Solar...

Area of Science:

• Materials Science
• Semiconductor Physics
• Renewable Energy

Background:

• Titanium oxide (TiO) is typically known as an electron-selective contact in semiconductor devices.
• Its function is attributed to a lower energy barrier for electrons compared to holes at the TiO/semiconductor interface.

Purpose of the Study:

• To investigate the antithetic function of titanium oxide nanolayers as hole-selective contacts.
• To demonstrate efficient surface passivation and hole extraction in silicon devices using TiO.
• To explore the potential for high-efficiency solar cells utilizing this novel contact.

Main Methods:

• Growth of ~5 nm titanium oxide nanolayers via atomic layer deposition (ALD) on crystalline silicon (Si) substrates.
• Fabrication of proof-of-concept solar cells using both n-type and p-type Si absorbers.
• Analysis of interfacial layers (TiOSi:H and SiO:H) and manipulation through ALD process and post-treatments (atomic hydrogen, oxygen annealing).

Main Results:

• Demonstrated titanium oxide nanolayers acting as efficient hole-selective contacts with excellent surface passivation.
• Achieved power conversion efficiencies exceeding 20% for proof-of-concept solar cells.
• Identified the critical role of interfacial layer composition (TiOSi:H, SiO:H) in enabling efficient hole extraction and passivation.

Conclusions:

• Titanium oxide nanolayers exhibit an antithetic function, serving as effective hole-selective passivating contacts.
• The composition of the TiO/Si interface, controllable via ALD and post-treatments, is key to performance.
• This finding presents an opportunity to replace conventional heterocontacts and dielectric passivation layers in various semiconductor devices.