Halogen-Bonded Hole-Transport Material Enhances Open-Circuit Voltage of Inverted Perovskite Solar Cells

Area of Science:

• Materials Science
• Photovoltaics
• Organic Chemistry

Background:

• Interfacial properties between hole-transport materials (HTMs) and perovskite layers are crucial for efficient charge transfer and perovskite crystal growth in inverted solar cells.
• Halogen bonding (XB) is a promising functional group for developing advanced small molecule HTMs.

Purpose of the Study:

• To synthesize and characterize a novel carbazole-based, iodine-functionalized HTM (O1) for perovskite solar cells.
• To investigate the impact of halogen bonding on the HTM-perovskite interface and device performance.

Main Methods:

• Synthesis of a novel iodine-functionalized HTM (O1) and a reference HTM (O2).
• Fabrication of inverted perovskite solar cells using O1 and O2.
• Experimental and theoretical studies to analyze interfacial interactions and charge dynamics.
• Device performance characterization, including power conversion efficiency (PCE) and operational stability.

Main Results:

• The synthesized O1 exhibits high hole mobility and suitable energy levels for perovskite alignment.
• Strong I···I⁻ halogen bonding interaction between O1 and perovskite forms an ordered interlayer.
• This XB-induced interlayer enhances charge extraction efficiency and suppresses non-radiative recombination by passivating surface traps.
• Devices with O1 show a significant increase in open-circuit voltage (up to 114 mV) and a PCE of 22.34% compared to the reference.

Conclusions:

• The novel iodine-functionalized HTM (O1) effectively utilizes halogen bonding to create an ordered interface with perovskite.
• This ordered interface significantly boosts device performance by improving charge dynamics and reducing recombination.
• The O1-based HTM demonstrates enhanced operational stability, highlighting its potential for efficient and durable perovskite solar cells.