Mitigating diffusion-length limitations in back-contact CZTSSe solar cells via synergistic field-effect engineering:...

Area of Science:

• Materials Science
• Renewable Energy
• Semiconductor Physics

Background:

• Interdigitated back-contact (IBC) solar cells offer advantages by eliminating front-surface parasitic absorption.
• Kesterite Cu2ZnSn(S,Se)4 (CZTSSe) solar cells face challenges with IBC architectures due to short minority-carrier diffusion lengths compared to electrode pitches.

Purpose of the Study:

• To numerically investigate a synergistic field-effect engineering strategy for quasi-interdigitated back-contact (QIBC) CZTSSe solar cells.
• To overcome the limitations imposed by minority-carrier diffusion length in applying IBC architectures to CZTSSe absorbers.

Main Methods:

• Two-dimensional TCAD simulations calibrated against a certified 14.9%-efficiency front-contact CZTSSe device.
• Implementation of negative fixed charges at the Al2O3/CZTSSe interface to create a hole accumulation layer.
• Utilizing asymmetric electrode geometry and full-thickness bandgap grading to enhance charge carrier transport.

Main Results:

• The simulated optimized QIBC CZTSSe solar cell achieved a power conversion efficiency of 15.75%.
• Key performance metrics included a short-circuit current density of 38.48 mA cm-2, open-circuit voltage of 606 mV, and fill factor of 67.5%.
• Sensitivity analysis identified critical material parameters (defect density < 10^14 cm-3, electron mobility > 40 cm^2 V^-1 s^-1) achievable with current technology.

Conclusions:

• Synergistic field-effect engineering is a viable strategy for developing high-efficiency back-contact kesterite solar cells.
• The QIBC design effectively addresses the minority-carrier diffusion length constraint in CZTSSe absorbers.
• This approach presents a promising pathway for advancing kesterite solar cell technology towards industrial relevance.