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Back Shallow Ge Gradient Enhanced Carrier Separation for CZTSe Solar Cells through a Coselenization Process
Jingling Liu1, Zhiwen Liu1, Kang Gao1
1Key Laboratory for Special Functional Materials of Ministry of Education, Collaborative Innovation Center of Nano Functional Materials and Applications, Henan University, Kaifeng 475004, Henan Province, People's Republic of China.
Implementing a shallow germanium (Ge) gradient in Copper Zinc Tin Sulfoselenide (CZTSSe) solar cells improved efficiency over 10%. This breakthrough offers a promising path for developing advanced Ge-involved solar cells.
Area of Science:
- Materials Science
- Renewable Energy
- Semiconductor Physics
Background:
- Gallium (Ga) gradients enhance Copper Indium Gallium Selenide (CIGSe) solar cells.
- Germanium (Ge) incorporation in Copper Zinc Tin Sulfoselenide (CZTSSe) solar cells is a promising strategy.
- Previous Ge-graded CZTSSe solar cells showed lower efficiency (9.2%) compared to non-graded (12.3%).
Purpose of the Study:
- To demonstrate a shallow Ge gradient in CZTSSe solar cells.
- To improve the efficiency of Ge-graded CZTSSe solar cells.
- To understand the mechanisms behind efficiency improvement.
Main Methods:
- A GeSe2-Se coselenization process was used to create the Ge gradient.
- GeSe2 acted as a low-temperature fluxing agent.
- Ge transport was induced towards the back interface.
Main Results:
- A shallow Ge gradient CZTSSe solar cell achieved over 10% efficiency.
- The Ge gradient was successfully implemented using the coselenization process.
- Relieved band tails and improved junction quality were observed.
Conclusions:
- The improved carrier separation is attributed to relieved band tails and better junction quality.
- This study represents a significant advancement for Ge-graded CZTSSe solar cells.
- The findings provide a viable approach for developing Ge-involved solar cells.
