European Commission
agence de communication Lyon

Ultrathin wafer development

Overall objective are to develop skills and processes to produce ultrathin wafers of below 50 micron thickness. In a first approach, classical wire sawing is used to achieve full-size wafers of <80 μm thickness suitable for cell and module processing. Main emphasis is however put on the objective to develop kerf-free wafers of <50 μm thickness using epitaxial processing and re-using of substrate templates. All ultrathin wafers developed in this JRA shall feature electronic and mechanical properties to allow for > 20% solar cells, which can be implemented into advanced modules.


Cell processing of ultrathin wafers

The objective is to develop a process for the preparation of the next generation of silicon solar cells based on ultra-thin monocrystalline wafers (40 to 80 μm) with 23.5% efficiency, 2 gram Si/Wp and <0,3 €/ Wp. The partners will work on an advanced solar cell structure dedicated to ultra-thin wafers, with a focus on the issues of light trapping, high surface passivation level and advanced metallization. The aim is to address main technological challenges and to prove some new optical and electrical improvement on ultra-thin silicon SINTEF reference substrates as well as lift off ultra-thin wafers.


Module development for ultrathin x-Si cells and thin-films

For wafer based crystalline-Si:

The main aim for the x-Si part of the project is to demonstrate the feasibility of making thin wafers, and processing them into cells and modules, using industrial processes. The cost reduction compared to current module technology is expected to be around 20%, leading to prices below 0.5 €/Wp. The cost target will depend on the obtained efficiency. Though the main aim is to demonstrate feasibility of ultra-thin x-Si wafers, cells and modules, the efficiency target for the ultra-thin wafer based cells is ambitiously put to 22% using industrial processing.


For thin-films:

Most thin-film solar cells consist of simple layer stacks of absorber material sandwiched between front and back contacts. The monolithic interconnection using three laser ablation steps are standard and well optimized for each technology. New device architectures and design of thin-film solar cells might require adaption of interconnection schemes. These will be developed in order to utilize the advantage of monolithical series connection also for new thin-film device structures. Thin-film solar modules have adopted the encapsulation technology from wafer-based modules. However, the requirements for and the features of the encapsulation are different. Thus, new and simple encapsulation methods are to be developed for state-of-the-art and new thin-film devices. The aim is high stability at cost reduction for the encapsulation by 20%.


Advanced light management for thin-film PV

The objective is to develop higher efficiency thin-film solar cells (e.g. Cu(In,Ga)(S,Se)2, TF-Si) with less solar cell base materials. To achieve this objective, the partners will work on advanced device concepts, on the processing and on the modeling. The focus will be on improved optical performance. Novel 3D architectures and photonic structures will be developed to achieve better light-trapping structures. Processes like nanoimprint and nanomolding will be integrated into the process chain of the solar cells. The novel structures will result in a higher absorptance in the solar cell. This will reduce material consumption by a 20% reduction of layer thickness. For TF-Si, two novel approaches will be followed. The first one will focus on the nano-patterning/nano-structuring of the cell itself. It is the aim that the novel processes used to structure the active layers maintain or improve the electrical properties (mainly the fill factor) of the device. In the second approach, flat grating structures will be developed to maintain or improve the optical properties with improved electrical performance (mainly Voc). With the reduced material consumption and enhanced efficiency, a cost reduction per Wp of 20% is expected for both thin-film technologies. These novel cell architectures are also expected to remove bottleneck for further efficiency improvements.


Very low-cost OPV

This JRA addresses the concept of encapsulation-less solar cells that offer a rationale strategy for developing stable solar cells based on the most stable materials and materials combinations apt for scaling up the production process. The objectives are: - To develop an encapsulation-less organic solar cell - To build the methodology to screen materials and layers combinations for enhanced stability - To use that innovation as platform for an encapsulated long-lived organic solar cell