Optimized Ni_1- Al O hole transport layer for silicon solar cells

Area of Science:

• Materials Science
• Solid State Physics
• Renewable Energy

Background:

• Hole transport layers (HTLs) are crucial for efficient p-i-n solar cell performance.
• Nickel Oxide (NiO) is a potential HTL material, but its properties require optimization.
• Aluminum alloying offers a route to tune NiO's electronic and transport characteristics.

Purpose of the Study:

• To investigate the stoichiometry, electronic properties, and interfacial band alignment of aluminum-alloyed NiO (Ni_1-xAl_xO).
• To evaluate Ni_1-xAl_xO as a hole transport layer (HTL) in p-i-n solar cells.
• To determine the optimal alloy composition and interface design for enhanced solar cell performance.

Main Methods:

• Component material and slab structural simulations.
• Simulated and measured angle-resolved valence-band photoemission spectroscopy (PES).
• Technology Computer-Aided Design (TCAD) device simulations.

Main Results:

• Work function of NiO increases with Al content, from 4.1 eV (pure NiO) to 4.7 eV (Al_0.50Ni_0.50O).
• Optimal band alignment achieved with a Ni-enriched interface, enabling staggering band alignment for charge separation.
• Disorder in Al-rich, non-annealed samples increases hole carrier self-energy by an order of magnitude.

Conclusions:

• Aluminum alloying effectively tunes the work function and electronic properties of NiO for HTL applications.
• A graded doping approach, with high Al content at the contact/oxide interface and low content at the oxide/semiconductor interface, is optimal.
• The findings provide a pathway for designing efficient HTLs for advanced solar cell architectures.