Squaric Acid-Containing Hole-Collecting Monolayer Materials for p-i-n Perovskite Solar Cells

Area of Science:

• Materials Science
• Renewable Energy
• Photovoltaics

Background:

• Hole-collecting materials are crucial for enhancing perovskite solar cell (PSC) performance.
• Existing hole-collecting monolayer (HCM) materials are structurally limited to electron-donating skeletons like carbazole and triarylamine.
• A need exists for novel, structurally diverse HCMs to advance PSC technology.

Purpose of the Study:

• To develop and investigate novel squaraine derivatives as hole-collecting monolayer (HCM) materials for p-i-n perovskite solar cells (PSCs).
• To explore the structure-property relationships of these squaraine derivatives, focusing on the impact of substituents.
• To evaluate the performance and stability of PSCs utilizing these new HCMs.

Main Methods:

• Synthesis of a series of squaraine derivatives featuring a squaric acid moiety linked to an indoline moiety.
• Characterization of the chemisorption behavior on transparent conducting oxide surfaces, noting the formation of hydrophilic monolayers.
• Fabrication and testing of p-i-n PSC devices using the synthesized squaraine derivatives as HCMs, analyzing device performance and stability.

Main Results:

• The synthesized squaraine derivatives formed stable, hydrophilic monolayers on transparent conducting oxide surfaces due to the polar carbonyl group of squaric acid.
• Systematic variation of substituents on the squaraine core influenced molecular electronic structure and device performance.
• PSC devices incorporating these squaraine derivatives achieved high power conversion efficiencies (PCEs) up to 22.1% with notable stability.

Conclusions:

• Squaraine derivatives based on a simple squaric acid skeleton are effective hole-collecting monolayer materials for high-performance PSCs.
• The developed materials offer a promising alternative to conventional HCMs, enabling efficient and potentially cost-effective PSC fabrication.
• This work expands the structural diversity of HCMs and highlights the potential of squaraine chemistry in photovoltaic applications.