Obviating the requirement for oxygen in SnO2-based solid-state dye-sensitized solar cells

Area of Science:

• Materials Science
• Renewable Energy
• Photovoltaics

Background:

• Organic semiconductors in solar cells offer stability if oxygen is below 1 ppm.
• Solid-state dye-sensitized solar cells (DSSCs) paradoxically require oxygen for efficient function.
• Oxygen deprivation leads to rapid loss of photovoltage and photocurrent in DSSCs.

Purpose of the Study:

• To identify the cause of oxygen dependence in solid-state DSSCs.
• To investigate the detrimental implications of this requirement on device stability.
• To develop a strategy for achieving long-term stability in oxygen-free conditions.

Main Methods:

• Characterization of solar cells in both air and oxygen-free atmospheres.
• Analysis of device architecture to pinpoint shunting pathways.
• Fabrication of devices with an added insulating interlayer.

Main Results:

• A direct metal-cathode to metal-oxide photo-anode contact creates a shunting path.
• This metal-metal oxide contact forms a Schottky barrier, which significantly lowers under anaerobic conditions during light absorption.
• Incorporation of a mesoporous aluminum oxide interlayer successfully blocked the shunting path.

Conclusions:

• The shunting path is responsible for the oxygen dependence and poor performance in anaerobic conditions.
• The aluminum oxide interlayer enables efficient operation in oxygen-free atmospheres.
• This breakthrough paves the way for long-term stable solid-state dye-sensitized solar cells.