ESR Insights into PDINO-Modified Interfaces in Perovskite Solar Cells

Area of Science:

• Materials Science
• Solid-State Physics
• Photovoltaics

Background:

• Perovskite solar cells (PSCs) have shown significant progress in efficiency and stability.
• Cathode interlayers, such as PDINO, are used to enhance electron extraction in inverted PSCs.
• The microscopic mechanisms behind PDINO's effectiveness are not fully understood.

Purpose of the Study:

• To elucidate the microscopic mechanisms of PDINO modification at the electron transporting layer (ETL)/metal cathode interface in PSCs.
• To provide direct evidence of charge-transfer processes using electron spin resonance (ESR) spectroscopy.

Main Methods:

• Electron spin resonance (ESR) spectroscopy was employed to observe charge states in ETL/PDINO/metal cathode structures.
• Systematic investigations were conducted using various ETLs and metal cathodes.

Main Results:

• ESR measurements demonstrated electron diffusion from the Ag cathode to the PC$_{61}$BM ETL through the PDINO layer.
• PDINO was shown to reduce the effective work function of Ag, facilitating Ohmic contact formation.
• The relationship between energy-level alignment and electron diffusion was clarified across different material combinations.

Conclusions:

• PDINO plays a crucial role in improving electron extraction by facilitating Ohmic contact formation.
• The study elucidates the microscopic charge-transfer processes induced by PDINO modification at the interface.
• Understanding these mechanisms can guide further optimization of PSC efficiency and stability.