Lattice mismatch alleviation in p-CdTe/n-Si heterostructure by surface engineering on Si substrate

Area of Science:

• Materials Science
• Solid State Physics
• Photovoltaics

Background:

• Cadmium telluride (CdTe) and silicon (Si) are key materials for tandem solar cells.
• Incompatible lattice and thermal expansion mismatch (CTE) cause strain at the CdTe/Si interface, hindering device performance.
• Surface treatments are crucial for improving the quality and integration of CdTe films on Si substrates.

Purpose of the Study:

• To investigate the effects of surface treatments on CdTe thin film growth on n-type silicon (n-Si) substrates.
• To optimize CdTe/Si integration for enhanced two-junction tandem solar cell applications.
• To analyze strain reduction and improved interface bonding through texturization and CdCl2 treatment.

Main Methods:

• Magnetron sputtering for CdTe thin film deposition.
• Potassium hydroxide (KOH) for n-Si substrate texturization.
• Cadmium chloride (CdCl2) treatment for interface strain reduction.
• X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX) for material characterization.

Main Results:

• CdCl2/CdTe/textured n-Si (txt-nSi) showed the lowest full width at half maximum (FWHM) and dislocation densities.
• SEM revealed conformal CdTe growth on pyramidal textured Si, enhancing light capture.
• EDX indicated a Te-rich composition in CdTe films, regardless of CdCl2 treatment.
• Improved morphology, grain boundary passivation, and significantly enhanced CdTe adhesion on n-Si were observed.

Conclusions:

• Surface texturization and CdCl2 treatment effectively improve CdTe thin film quality on Si substrates.
• Reduced interfacial strain and enhanced adhesion are critical for successful CdTe/Si integration.
• This study presents a viable method for improving CdTe/Si tandem solar cell efficiency through optimized surface engineering.