The project FaWB ChaLT focuses on the development of wide-bandgap chalcopyrite solar absorber materials and devices for the prospective, new, and innovative chalcopyrite/Si tandem solar cells. These chalcopyrite/Si tandem solar cells can be reliable, cost-effective, and environmentally friendly. For such an innovative tandem cell design, the top cell absorber is made of wide-bandgap chalcopyrite material, and the bottom cell absorber is made of low-bandgap crystalline or multicrystalline Si. However, the experimental demonstration of such a new high-efficiency tandem solar cell device is limited by the fabrication temperature of chalcopyrite materials. In general, chalcopyrite semiconductors are deposited at high temperatures close to 600°C. The use of such high temperatures when creating a monolithic tandem configuration with Si solar cells degrades the bottom Si cell material layers, negatively affecting the overall performance of the resulting tandem solar cell. Another challenge is the use of toxic CdS material in chalcopyrite solar cell devices, which needs to be replaced with an environmentally friendly material. Furthermore, the design aspects of monolithic integration of wide-bandgap chalcopyrite materials with Si cell structures must be improved while overcoming these challenges.
The following are the overall objectives of the project.
(i) Tailor the chalcopyrite absorber composition by incorporating Ag to partially replace Cu, forming the wide-bandgap (Ag, Cu)(In, Ga)Se2. Investigate the role of Ag in reducing the deposition temperature. The first approach is to test the effectiveness of Ag in lowering the deposition temperature of known low-bandgap compositions and then extend the findings to produce advanced wide-bandgap chalcopyrite compositions.
(ii) Replace the traditional toxic CdS buffer layers typically used in chalcopyrite solar cells with alternative environmentally friendly oxide materials.
(iii) Introduce advanced tandem cell architecture to improve the integration of wide-bandgap chalcopyrite with Si structures, avoiding the degradation of Si cell quality.
