CdS/CdTe Heterostructures for Applications in Ultra-Thin Solar Cells.

Area of Science:

• Materials Science
• Photovoltaics
• Thin Film Technology

Background:

• Ultra-thin semi-transparent solar cells face challenges like inter-diffusion and incomplete surface coverage due to their minimal thickness.
• Applications in windows and transparent roofs require precise control over thin film deposition.

Purpose of the Study:

• To optimize the deposition of ultra-thin tin oxide (SnO₂), cadmium sulfide (CdS), and cadmium telluride (CdTe) films for solar cells.
• To investigate the impact of an undoped SnO₂ buffer layer on the performance of heterostructured solar cells.

Main Methods:

• Radiofrequency (RF) magnetron sputtering was used to deposit undoped SnO₂, CdS, and CdTe thin films.
• Preparation conditions were optimized for good surface coverage, absence of pinholes, and controlled growth rates.
• Heterostructured solar cells were fabricated, with and without an additional SnO₂ buffer layer between conductive glass and CdS.

Main Results:

• Optimized deposition conditions yielded thin films with excellent surface properties and controlled thickness.
• Incorporation of an undoped SnO₂ buffer layer between conductive glass and CdS significantly enhanced performance.
• Short-circuit current increased by 19%, and open-circuit voltage improved by 32% with the buffer layer.

Conclusions:

• The SnO₂ buffer layer effectively passivates the SnO₂/CdS interface, potentially blocking impurity diffusion.
• Improved band alignment at the interface is another likely factor contributing to enhanced solar cell performance.
• The study demonstrates a viable method for improving ultra-thin solar cell efficiency using a buffer layer.