Efficiency enhancement of thin films solar cells via CdS replacement and CZTSSe layer engineering (EECSC-23)

Project Director: Dr. Mohamed Yassine ZAKI

Acronym: EECSC-23

Project code: PN-III-P1-1.1-PD-2021-0240

Project Director: Dr. Mohamed Yassine Zaki

Project advice: National

Framework program of the project: P1 - Development of the national CD system - Human resources - Postdoctoral research projects (PD)

Funded by: Executive Unit for the Financing of Higher Education, Research, Development and Innovation, UEFISCDI

Contractor: National Institute og Materials Physics

Status: Ongoing

Start date: 01.04.2022

Closing date: 31.03.2024


Kesterite Cu2ZnSn(S,Se)4 (CZTSSe) based solar cells have attracted a lot of interest lately due to their promising potential and similar properties to the better known Cu(In,Ga)Se2 (CIGS) and CdTe photovoltaic devices. However, these materials suffer from the omnipresence of several secondary phases that influence their performances. The champion device has a 12.6% power conversion efficiency, which is still much lower than its counterpart CIGS. The objective of this project is the enhancement of the efficiency of CZTSSe thin films solar cells via PN junction layers engineering. The CZTSSe p-type absorber layers will be deposited using a two-steps magnetron sputtering deposition followed by a sulfurization/selenization in order to avoid the secondary phases and obtain stoichiometric films. Cadmium sulfide (CdS) is commonly used as a n-type layer for kesterite solar cells, but owing to Cd toxicity, ZnS or ZnSe materials are proposed here. Tuning the band alignment at the interface between the p-type and n-type layers will be done by varying the thickness and band gap of the buffer layer in order to achieve high efficiency CZTSSe solar cells. The findings of this project will be useful to understand the relation between the synthesis conditions, composition and the formation of secondary phases. This will guide the design of new ecological solar cells with an improved efficiency that can reach the commercial panels requirements.


- Synthesis of pure and highly crystalline CZTSSe thin films with the adequate stoichiometry and no secondary phases.
- Substitute the usual toxic buffer layer material (CdS) with a eco-friendly compound (ZnS/ZnSe).
- Fabrication of high efficiency solar cells using the elaborated CZTSSe absorber and ZnS/ZnSe buffer layers.

Estimated result:

- Recipe development of CZTSSe thin films without secondary phases.
- Investigating the use of ZnS and ZnSe buffer layers in kesterite solar devices.
- Finding solutions for PCE enhancement of the CZTSSe-based solar cells;
- Publication of two ISI articles.

Project Director: Dr. Mohamed Yassine Zaki (U-2000-066W-2802)

Project Mentor: Dr. Lucian Pintilie

This project aimed to improve thin film solar cells by exploring new materials and methods to make them more efficient and environmentally friendly. We focused on a material called CZTSSe, which is composed of abundant and eco-friendly elements, offering a sustainable alternative to traditional solar cell materials. Our goal was to replace toxic compounds like CdS with safer options, like ZnS or ZnSe, as buffer layers in the solar cells. Our objective was to explore the potential of using these buffer layers to improve the performance of solar cells. Throughout the project, we made significant progress in synthesizing CZTSSe thin films and testing different buffer layer materials. While we encountered challenges along the way, our efforts have provided valuable insights into how to make solar panels even better for the future.



Stage I summary:

The PN-III-P1-1.1-PD-2021-0240 project (contract no. PD 41) is dedicated to the realization of solar cells based on CZTSSe using a Cd-free buffer layer. Stage I of PN-III-P1-1.1-PD-2021-0240 (2021.04.01 - 2021.12.31) aims objectives are: (1) Understanding the fundamental reasons for the coexistence of the secondary phases and proposing solutions to avoid them, and also find answers to stoichiometry problems (2) Synthesis of single-phase and stoichiometric CZTSSe absorbing layers and (3) Structural, morphological, optical, compositional and electrical characterization of the obtained CZTSSe films.

Delivered results:

1 Oral presentation at Advanced Functional Materials for Optical, Laser and Photovoltaic Applications, Kenitra, Morocco;
1 Summer School Participation (invited) at the PaNOSC Summer School - Materials Science at Large Scale European Infrastructures Using Open and Fair Data, Szeged, Hungary;
3 Articles published in journals indexed in Web of Science®, with impact factor.

2022: SYNTHETIC SCIENTIFIC REPORT no. 1 in .pdf format is available at UEFISCDI and can be accessed upon request.


Stage II summary:

The stage II of the PN-III-P1-1.1-PD-2021-0240 project (contract no. PD 41) centers on the optimization of the ZnS buffer layer specifically designed for CZTSSe absorber layers in solar cells. The primary focus is to study and analyze the properties of the ZnS\CZTSSe junction. Subsequently, the findings were utilized in the fabrication of solar cells based on this optimized ZnS\CZTSSe heterojunction. The ultimate goal is to enhance the efficiency and functionality of these solar cells by leveraging the optimized interface between the ZnS buffer layer and the CZTSSe absorber layers.

Delivered results:

1 Poster presentation at international conference, (Tallin, Estonia).
3 Articles published in journals indexed in Web of Science, with impact factor.

1 Short Term Scientific Mission (STSM) at Polytechnic University of Barcelona - Efficiency enhancement of chalcogenide thin film solar cells via absorber layer engineering, Barcelona, Spain.

2023: SYNTHETIC SCIENTIFIC REPORT no. 2 in .pdf format is available at UEFISCDI and can be accessed upon request.


Stage III summary:

Phase III of the PN-III-P1-1.1-PD-2021-0240 project focused on the fabrication and characterization of solar cells using the CZTSSe absorber layers and ZnS/ZnSe buffer layers developed in earlier stages. The objective was to enhance CZTSSe-based solar cell efficiency. Strategies were explored to optimize device architecture and interface engineering. The goal was to identify key factors influencing performance and propose solutions for improved efficiency.

Delivered results:

1 Articles published in journals indexed in Web of Science, with impact factor.

2024: FINAL SCIENTIFIC REPORT in .pdf format is available at UEFISCDI and can be accessed upon request.

Articole publicate in jurnale cotate Web of Science®:

1. M.Y. Zaki, F. Sava, I.D. Simandan, A.T. Buruiana, C. Mihai, A. Velea, A.C. Galca, Effect of the stacking order, annealing temperature and atmosphere on crystal phase and optical properties of Cu2SnS3, Sci. Rep. 12 (2022) 7958. 10.1038/s41598-022-12045-3

2. M.Y. Zaki, F. Sava, I.D. Simandan, A.T. Buruiana, I. Stavarache, A.E. Bocirnea, C. Mihai, A. Velea, A.C. Galca, A two-step magnetron sputtering approach for the synthesis of Cu2ZnSnS4 films from Cu2SnS3\ZnS stacks, ACS Omega 7 (2022) 23800–23814. 10.1021/acsomega.2c02475

3. M.Y. Zaki, F. Sava, I.D. Simandan, A.T. Buruiana, C. Mihai, A. Velea, A.C. Galca, Cu2SnSe3 phase formation from different metallic and binary chalcogenides stacks using magnetron sputtering,  Mater. Sci. Semicond. 153 (2023) 107195. 10.1016/j.mssp.2022.107195

4. M.Y. Zaki, F. Sava, I.D. Simandan, A.T. Buruiana, A.E. Bocirnea, I. Stavarache, A. Velea, A.C. Galca, L. Pintilie, From non-stoichiometric CTSe to single phase and stoichiometric CZTSe films by annealing under Sn+Se atmosphere, Ceramics International 49 (2023), 33692-33702. 10.1016/j.ceramint.2023.08.056.

5. D.S. Catana, C.A. Parloaga, M.Y. Zaki, F. Sava, I.D. Simandan, A.T. Buruiana, A. Velea, Formation and detection of secondary crystalline phases in Cu2SnS3 thin films for photovoltaic applications, Romanian Reports in Physics 75, 504 (2023). 10.59277/romrepphys.2023.75.504.

6. D.S. Catana, M.Y. Zaki, F. Sava, I.D. Simandan, A.T. Buruiana, A. Velea, Understanding the Effects of Post-Deposition Sequential Annealing on the Physical and Chemical Properties of Cu2ZnSnSe4 Thin Films, Surfaces 6(4) (2023), 466-479. 10.3390/surfaces6040031.

7. Y. Zaki, A. Velea, “Recent Progress and Challenges in Controlling Secondary Phases in Kesterite CZT(S/Se) Thin Films: A Critical Review”. Energies 17 (2024), 1600. 10.3390/en17071600.

Dr. Mohamed Yassine Zaki

National Institute of Materials Physics

Laboratory of Complex Heterostructures and Multifunctional Materials

405A Atomistilor street

077125, Magurele, Romania

E-mail: yassine.zaki@infim.ro

Mobile: +40729461966


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