Highly Air Stable Tin Halide Perovskite Photovoltaics using a Bismuth Capped Copper Top Electrode

Area of Science:

• Materials Science
• Renewable Energy
• Photovoltaics

Background:

• Organo-tin halide perovskites offer potential for efficient solar energy conversion.
• Stability remains a critical challenge for their commercial viability, especially in unencapsulated devices.
• Degradation pathways often involve cathode corrosion and iodine-induced damage.

Purpose of the Study:

• To develop an effective strategy for enhancing the operational stability of inverted organo-tin halide perovskite photovoltaics.
• To investigate the role of a bismuth capping layer in protecting photovoltaic devices.
• To understand the mechanism by which bismuth improves device longevity.

Main Methods:

• Fabrication of inverted organo-tin halide perovskite solar cells.
• Incorporation of a thin bismuth layer as a cathode cap.
• Performance and stability testing under continuous one-sun illumination in ambient air with electrical load.
• Analysis of degradation mechanisms and the interaction of bismuth with iodine gas.

Main Results:

• Unencapsulated devices with bismuth capping retained up to 70% of peak power conversion efficiency after 100 hours of testing.
• The bismuth layer effectively blocked cathode corrosion by iodine gas.
• Bismuth sequestered iodine gas by promoting its deposition on the capping layer, away from active device components.
• High affinity of iodine for bismuth was correlated with bismuth's polarizability and crystal face.

Conclusions:

• A bismuth capping layer is a simple yet highly effective method to enhance the stability of organo-tin halide perovskite photovoltaics.
• Bismuth acts as a protective barrier and iodine scavenger, significantly improving device longevity under operational stress.
• The environmentally benign, cost-effective, and easily deposited nature of bismuth makes it an ideal material for stabilizing perovskite solar cells.