Solution-Processed Thickness-Insensitive Molybdenum Oxide Hole-Transporting Layer Regulated by Reductive Ionic Liquid...

Area of Science:

• Materials Science
• Organic Electronics
• Renewable Energy

Background:

• Developing efficient and stable hole-transporting layers (HTLs) is crucial for high-performance organic solar cells (OSCs).
• Traditional HTLs like PEDOT:PSS face challenges in conductivity, stability, and thickness insensitivity for scalable OSC manufacturing.
• Solution-processed molybdenum oxide (MoO_x) is a potential alternative but requires performance enhancement.

Purpose of the Study:

• To develop a solution-processed, thickness-insensitive HTL for high-performance and scalable OSCs.
• To enhance the conductivity and electronic properties of MoO_x HTLs.
• To investigate the potential of n-doped MoO_x with ionic liquids as a superior alternative to PEDOT:PSS.

Main Methods:

• Synthesized n-doped molybdenum oxide (MoO_x) by treating ammonium heptamolybdate with a reductive ionic liquid (IL).
• Characterized the conductivity and electronic properties of the resulting 5% IL:MoO_x material.
• Fabricated organic solar cells using the 5% IL:MoO_x HTL and evaluated their power conversion efficiency (PCE), stability, and thickness dependence.

Main Results:

• Achieved a significantly enhanced conductivity of 8.06 × 10^-3 S m^-1 for the 5% IL:MoO_x HTL.
• Demonstrated a remarkable PCE of 19.55% in a D18:N3:L8-BO ternary OSC system, outperforming neat MoO_x and PEDOT:PSS devices.
• Showcased superior device stability and maintained 83.3% of optimal PCE at a thickness of 150 nm, indicating excellent thickness insensitivity.

Conclusions:

• The n-doped IL:MoO_x HTL offers a highly conductive, stable, and versatile solution-processed alternative for OSCs.
• This material significantly improves OSC performance and addresses key challenges in scalability.
• The developed HTL holds great potential to replace PEDOT:PSS in the commercial production of organic solar cells.