27.09%-efficiency silicon heterojunction back contact solar cell and going beyond

Area of Science:

• Photovoltaics
• Materials Science
• Semiconductor Physics

Background:

• Crystalline-silicon heterojunction back contact solar cells (HBC SCs) are at the forefront of solar energy technology.
• Achieving high efficiency in HBC SCs is challenged by charge carrier recombination and transport limitations.

Purpose of the Study:

• To develop highly efficient HBC SCs using laser patterning.
• To identify and address the primary sources of recombination losses.
• To optimize cell design for improved performance.

Main Methods:

• Utilized laser patterning to fabricate HBC SCs.
• Analyzed recombination losses at hole-selective contacts and polarity boundaries.
• Investigated the impact of rear-side pattern design on contact resistivity and series resistance.
• Evaluated carrier recombination at the wafer edge.

Main Results:

• Achieved a certified efficiency of 27.09% for HBC SCs.
• Identified hole-selective contact region and polarity boundaries as primary recombination sites.
• Established a correlation between contact resistivity, series resistance, and rear-side pattern design.
• Demonstrated that wafer edge recombination becomes dominant after mitigating electrical shading.

Conclusions:

• Laser patterning is an effective technique for producing high-efficiency HBC SCs.
• Addressing recombination at the hole-selective contact and wafer edge is crucial for further efficiency gains.
• Optimization of passivation, anti-reflection coatings, and reflectors can lead to efficiencies as high as 27.7%.