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Applying silicon solar cell technology to revolutionize the design of thin-film solar cells and enhance their efficiency, cost and stability

Periodic Reporting for period 2 - Uniting PV (Applying silicon solar cell technology to revolutionize the design of thin-film solar cells and enhance their efficiency, cost and stability)

Reporting period: 2018-09-01 to 2020-02-29

Thin film (TF) photovoltaics (PV) hold high potential for Building Integrated PV, an important market as European buildings require to be nearly zero-energy by 2020 [1]. Currently, Cu(In,Ga)(S,Se)2 (= CIGS(e)) TF solar cells have high efficiency, but also a simple one-dimensional cell design with stability and reliability concerns.
- Scientifically, Uniting PV aims to study the practical boundaries of CIGS(e) TF solar cell efficiency.
- Technologically, the project targets to establish a solar cell with: Increased cell efficiency; improved stability and reliability, due to reduced CIGS(e) thickness and passivation layers hindering alkali metal movement; and reduced cost, due to the use of less Ga and In, and industrially viable materials, methods and equipment.
Hence, its outcome will be (up)scalable, valuable for other TF PV materials, and start a new wave of innovation in and collaboration between TF and silicon (Si) PV research fields.

The main target is to revolutionize the design of CIGS(e) solar cells through implementation of advanced three-dimensional Si solar cell concepts (see attached image). This novel design consists of surface passivation layers and light management methods integrated into ultra-thin (UT) CIGS(e) solar cells.

2 PhD students have been working on the development of - front and rear - surface passivation layers and light management methods, and 1 PhD student on thinning down and simplification of the absorber layer. A Postdoc assisted the PI in the guidance of these PhD researchers.
Current progress beyond the state of the art
- Surface cleaning treatments, and industrially viable contacting approaches
- Metallic reflectors combined with surface passivation layers
- Simplified absorber layers for improved reliability/stability, new electrical characterization approach for thin film PV

Expected results until the end of the project
Scientifically – This project will deliver new understanding about ultra-thin CIGS(e) materials and its surface passivation and optical confinement. This includes new scientific models for passivation and light management, and complete solar cell models, but also novel characterization devices and approaches.
Technologically – If the proposed CIGS(e) solar cell design is effective, it will also be interesting for other TF PV materials, e.g. cadmium telluride (CdTe) and perovskite, two materials with very similar characteristics. Additionally, the concept will certainly be up-scalable due to a clear focus on industrial viability throughout the complete project. Finally, many other state-of-the-art Si PV concepts will become interesting for application in TF PV.
Socially – Currently, the field of PV is noticeably divided in two very independent parts, i.e. silicon and thin film. Both parts have their own researcher profile, technological approaches and industrial establishment. If “Uniting PV” is successful, both fields must start to show interest in each other, which should have a very positive impact on collaboration and innovation. Hence, two very competitive solar cell technologies and industries could develop important synergies, e.g. on the level of required equipment and solar cell architectures