Photovoltaics International Papers

Solar cell production in 2018 represented change on many fronts, but may be remembered as a year during which Chinese-owned companies made further strategic moves as part of the current Beijing mandate to position the country as a high-tech manufacturing global powerhouse. This article explains how this is having a dramatic impact on solar cell manufacturing outside the control of leading Chinese-funded companies, and what this really means in terms of solar cell technologies and industry-wide technology roadmaps during 2019.

Bifacial PV promises a significant reduction in the levelized cost of electricity (LCOE) for PV systems, which, compared with efficiency improvements at the cell level, is still achievable with comparatively moderate effort. Almost all major PV module suppliers have bifacial modules in their product portfolios or have announced production. This paper gives an overview of the currently available bifacial modules and cell technologies and the performance of these modules. Special attention is given to the cells and the layout of the modules, including light trapping and interconnection technologies, the encapsulation materials and the adapted mounting solutions. Finally, an outlook is given on the basis of the compiled information.

In the evolution towards higher cell efficiencies, new cell concepts (twosided and back contacted) have been introduced and for each of these concepts, new module materials and interconnection technologies have to be developed to fulfil all the demands of a good end product in terms of lowest costs, highest yield and power and above all superior quality (reliability and durability). There is no single module concept that fits all cell concepts or module application type so existing module concepts need to be adapted or innovative module technologies are required to fit the aforementioned requirements. This paper provides an overview summarizing the recent developments of integrated cell to module manufacturing approaches such as multi-busbar, multi-wire, half-cell and shingling technologies for two-side contacted cells and advanced soldering, woven fabric and foil based module technologies for back contacted cells aiming for the highest power outputs, lowest costs and longest lifetimes.

The EU Horizon Sharc25 project has provided deep insights into highly efficient Cu(In,Ga)Se2 (CIGSe) thin-film solar cells fabricated by lowand high-temperature co-evaporation using advanced characterization methods, analytical tools, device simulation, and density functional theory modelling. This complementary approach led to a continuous knowledgedriven development and improvement of the CIGSe absorber. Based on optimized chemical composition, profiles, and alkali metal post-deposition treatments (PDT) using KF, RbF, and CsF, the CIGSe cell efficiency could be substantially increased to a record value of 22.6%. Due to additional modifications at the absorber/emitter (replacement of standard buffer system by a combination of thin CdS and TiO2) and back contact/ absorber (introduction of Al back reflector in combination with InZnO diffusion barrier) interfaces, in particular the short-circuit current could be increased. Furthermore, passivation layers in combination with point contact schemes at the CIGSe front and back side were developed and are still under investigation.

Silicon heterojunction (SHJ) solar cells demonstrate a high conversion efficiency, reaching up to 25.1% using a simple and lean process flow for both-sides-contacted devices, and achieving a record silicon solar cell efficiency of 26.7% in back-contacted configuration. In addition, the field advantages of SHJ cell technology are a native bifaciality and low thermal coefficient providing impressive energy yield. Finally, the technology demonstrates potential cost reduction as it is perfectly suited for thin wafers integration. The SHJ technology is therefore today triggering strong interest in the PV industry, appearing on the roadmap of different cell manufacturers, with several production lines and pilot lines being installed worldwide. One limiting factor of the technology is related to the metallization: due to temperature restrictions on heterocontacts, the standard firing through silver paste needs to be replaced by low curing temperature paste. This type of pastes yield fingers with higher bulk resistivity (two to three times the one obtained with high temperature cured silver pastes) and lower adhesion after soldering. In this paper, materials, processes and costs figures will be reviewed for the metallization and module integration of SHJ solar cells, with a focus on copper plating benchmarked to silver screen-printing, for varying module interconnection technologies.

Improving PERC cells requires rather different strategies than standard cells have required, demanding concrete improvements in materials, manufacturing procedures and fabrication tools.

Improving the texturing approach for diamond wire-sawn (DWS) multicrystalline silicon (mc-Si) wafers is one of the key steps to decrease its efficiency gap with monocrystalline silicon-based solar cells. In this regard, black silicon texturing has increasingly caught attention of both academia and industries as a potential approach towards mass production of high-efficiency mc-Si solar cells. In this paper, the challenges of implementing such a texture, with unique feature sizes, in mass production are discussed in detail, and the latest results are reviewed. Finally, results of the first trials at high volume manufacturer applying an alternative plasma-less dry-chemical etching (ADE) method are presented.

PV manufacturing capacity expansion announcements in the second quarter of 2018 were slightly higher than the previous quarter, although activity slumped specifically in June, following China’s decision to suddenly cap utility-scale and distributed generation projects. The quarter was also characterized by activity in India, partially driven by a major Chinese manufacturer. The report will also analyze first half year capacity expansion plans and targeted locations, globally.

After defining the term Industry 4.0 according to the authors’ interpretation, this paper elaborates on the opportunities and challenges that the Industry 4.0 transition will bring to the PV sector. The topic is approached from various angles. How can the PV industry and the related value chain itself progress to Industry 4.0? And how does this reflect in different application sectors, such as construction and automotive? This paper presents a future scenario towards which the industry could be heading; some of the steps already being taken and some of the main challenges ahead are described. The value of PV technology as an enabler for other sectors, such as edge versus cloud computing, to move into Industry 4.0 is also touched upon. Additionally, a number of enablers and boundary conditions are highlighted in the context of Industry 4.0 and their relevance to the PV industry (legislation, cyber security, etc.) The status of Industry 4.0 in PV compared with other sectors is also explored. Wherever appropriate and possible, examples of projects and activities that illustrate the described topics are given.

An analysis of R&D spending of 20 publicly listed PV module manufacturers in 2017 has been undertaken to replace Photovoltaics International’s previous list of 12 companies tracked over a 10-year period. A number of the original companies tracked have subsequently de-listed from stock markets and gone private, which meant that a broader analysis, including other listed companies was required to provide a good representation of global R&D spending trends in the PV wafer, cell and module segments of the upstream solar market.