Back-Surface Passivation of CdTe Solar Cells Using Solution-Processed Oxidized Aluminum.

Area of Science:

• Materials Science
• Photovoltaics
• Surface Chemistry

Background:

• Back-surface passivation is critical for high-efficiency solar cells.
• Effective passivation strategies for Cadmium Telluride (CdTe) photovoltaics remain underexplored.

Purpose of the Study:

• To develop and validate a solution-based process for back-surface passivation of CdTe solar cells.
• To investigate the impact of aluminum oxide species on CdTe device performance and electrical properties.

Main Methods:

• Deposition of oxidized Al3+ species onto the back surface of CdTe devices using a solution-based method.
• Optimization of Al3+ deposition amount to achieve surface-specific passivation.
• Characterization of device performance, including open-circuit voltage (Voc), fill factor (FF), and photoconversion efficiency (PCE).
• Utilized time-resolved photoluminescence and quantum efficiency measurements to analyze interface recombination.

Main Results:

• A surface-specific passivation effect was achieved with approximately one monolayer of Al3+ species, leading to increased Voc, optimized FF, and PCE.
• Exceeding this optimal amount resulted in a blocking alumina-like layer, decreasing FF and PCE.
• The optimized process improved baseline PCE for both copper-free and copper-doped CdTe devices.
• The greatest efficiency improvement (from 12.6% to 14.4%) was observed when Al3+ was deposited before CdCl2 activation and copper doping.

Conclusions:

• Solution-based deposition of specific amounts of aluminum species offers an effective method for back-surface passivation in CdTe photovoltaics.
• This technique significantly reduces interface recombination, leading to enhanced device performance and higher photoconversion efficiencies.
• The findings provide a pathway for improving CdTe solar cell efficiency, particularly when integrated with copper doping and optimized processing steps.