Photocurrent mapping of 3D CdSe/CdTe windowless solar cells.

Area of Science:

• Materials Science
• Solid-State Physics
• Photovoltaics

Background:

• Thin-film photovoltaic devices are crucial for renewable energy.
• Understanding localized performance limitations is key to improving efficiency.
• CdSe/CdTe heterostructures offer potential for low-cost solar energy conversion.

Purpose of the Study:

• To investigate the localized current collection efficiency of patterned CdSe/CdTe thin-film photovoltaic devices.
• To identify performance-limiting factors at the submicrometer scale.
• To evaluate the impact of surface passivation on device performance.

Main Methods:

• Fabrication of thin-film photovoltaic devices with interdigitated comb electrodes.
• Electrodeposition of CdSe and pulsed laser deposition of CdTe.
• Application of scanning photocurrent microscopy (SPM) for submicrometer analysis.
• Assessment of device performance before and after ammonium sulfide passivation.

Main Results:

• SPM revealed "dead zones" above the back contact electrodes, indicating recombination losses.
• These "dead zones" were identified as a primary performance limitation in windowless CdSe/CdTe devices.
• Ammonium sulfide passivation significantly improved device performance.
• Passivation enabled the thin-film photovoltaic devices to achieve a power conversion efficiency of 4.3% under AM1.5 illumination.

Conclusions:

• Scanning photocurrent microscopy is an effective tool for diagnosing performance issues in thin-film solar cells.
• Recombination at the back contact is a critical factor affecting CdSe/CdTe device efficiency.
• Ammonium sulfide passivation offers a viable strategy for enhancing the efficiency of these photovoltaic devices.