How Do Surface Polar Molecules Contribute to High Open-Circuit Voltage in Perovskite Solar Cells?

Area of Science:

• Materials Science
• Renewable Energy
• Photovoltaics

Background:

• Improving open-circuit voltage (V_OC) is crucial for advancing perovskite solar cell (PSC) performance.
• Surface modification using organic ammonium halides is a known strategy to reduce defects and enhance V_OC.
• The precise mechanism behind the V_OC enhancement in PSCs remains incompletely understood.

Purpose of the Study:

• To investigate the role of polar molecules in enhancing the V_OC of perovskite solar cells.
• To elucidate the underlying mechanism responsible for the V_OC improvement.
• To demonstrate the potential for achieving higher efficiencies in PSCs through surface modification.

Main Methods:

• Application of polar molecular phenmethylammonium ions (PMA+) at the perovskite/hole transporting layer interface.
• Characterization of the resulting perovskite solar cell devices.
• Analysis of surface passivation effects and quasi-Fermi level splitting.

Main Results:

• A significant increase in V_OC of over 100 mV was achieved, reaching 1.175 V.
• The PMA+ treatment effectively passivated surface defects via a surface dipole effect.
• The enhanced V_OC resulted from combined defect suppression and improved hole quasi-Fermi level splitting, leading to a 24.10% device efficiency.

Conclusions:

• Surface polar molecules, specifically PMA+, contribute significantly to achieving high V_OC in PSCs.
• A fundamental mechanism involving surface dipole creation and defect passivation is proposed for V_OC enhancement.
• This approach offers a pathway toward developing highly efficient perovskite solar cells with further voltage improvements.