Photovoltaics International Papers

PV CellTech has become the upstream PV industry’s foremost annual event. This year, a key topic for discussion was whether n-type silicon would trump p-type as manufacturers look to drive up efficiencies, as well as the inevitable debate over the relative fortunes of multi and mono technologies. Tom Kenning reports from the event.

Two factors have coincided to stimulate the recent spur in interest for hybrid tandem PV technology based on crystalline silicon – the fact that balance-of-system (BOS) costs are increasingly dominating turnkey system costs, which strengthens the effect of high efficiency in reducing Wp costs, and the discovery of perovskite solar cells as a promising low-cost wide-band-gap partner for crystalline silicon (c-Si). This paper presents the progress and analysis of four-terminal (4T) perovskite/c-Si tandem technology at ECN part of TNO, with perovskite technology development carried out within the Solliance research organization.

PV manufacturing capacity expansion announcements in the first quarter of 2018 continued to mirror those of the previous two years, highlighting the recent trend of the last quarter and the first quarter of each year (since the end of 2015) being the most active. The quarter being discussed also represents a revival in thin-film expansion plans, the return of PV module assembly outpacing solar cell announcements and the return of India and the US as major destinations for new capacity plans.

As the PV industry strives to reach terawatt scale, addressing the last remaining cost centres of the crystalline silicon value chain will play a critical role in ensuring that the industry can continue to achieve lower systems costs, and provide the extremely low levelized cost of electricity (LCOE) required to drive the adoption of this form of energy. Wafer manufacturing remains the single largest cost driver in industrial cell production. While incremental improvements, such as diamond wire (DW) sawing, have helped to lower silicon consumption, wafer manufacturing has lacked the significant step change necessary for achieving dramatic cost reduction.

State-of-the-art black-silicon texturing technology has been successfully implemented in all of the 4.5GW multi-Si cell production lines at Canadian Solar (CSI). With a combination of black-silicon texturing and diamondwire-sawn wafers, it has been possible to increase cell efficiency and wattage, while significantly reducing the cost. To further improve CSI’s multi-Si product performance and cost, multi-Si passivated emitter rear contact (multi-PERC) technology has been developed to achieve a mass production cell efficiency of more than 20% on average, and a module power exceeding 300W. By the end of 2017, a production capacity of over 1GW had been established, and CSI’s majority multi-Si cell capacity will be upgraded to PERC in 2018. This paper will introduce the solutions to realizing light-induced degradation (LID)-controlled multi-PERC cells and modules, as well as offering a discussion of the degradation performance. In addition, the technology evolution of CSI’s high-efficiency multi-Si products and a roadmap for 22%-efficiency multi-Si cells are presented.

The extra energy gain offered by bifacial PV modules has helped make them an increasingly popular choice in the global PV industry. But the question of how to define, measure and rate the electrical output from bifacial modules is a hotly debated topic, given the extent to which the rear-side contribution is dependent on a range of variable factors relating to local environmental conditions and system configurations. Drawing on in-house modelling and simulation software developed at TÜV Rheinland, this paper explores the power rating issue for bifacial devices, examining the definitions of rear irradiance, measurement test method, power stabilization and verification for type approval. Relevant reliability and safety tests are discussed, with additional modifications and suggestions for bifacial PV modules.

Crystalline silicon heterojunction (HJT) solar cells and modules based on amorphous silicon on monocrystalline wafers offer advantages over established wafer-based technologies in terms of efficiency potential, complexity of the manufacturing process, and energy yield of the modules. The temperature sensitivity of these solar cells, however, poses considerable challenges for their integration in modules. Currently, there exist three approaches for the interconnection of HJT solar cells, each with its own strengths and weaknesses: 1) ribbon soldering with low-meltingpoint alloys; 2) gluing of ribbons by using electrically conductive adhesives (ECAs); 3) SmartWire Connection Technology (SWCT).

TOPCon is regarded as a possible follow-up technology to the passivated emitter and rear cell (PERC) concept. This paper presents the latest results for high-efficiency solar cells, and the progress made on migrating layer deposition to high-throughput tools, which are already in use in industry. Possible metallization approaches, and three different industrially relevant solar cell structures featuring TOPCon, are also discussed.

The in-house market research team at PV Tech, this journal’s sister website, has developed a new model for forecasting trends in polysilicon consumption by the solar industry. This article analyzes how, based on this new model, the industry’s use of polysilicon will dip below 4 grams per watt by the end of this year.

To realize power generation everywhere, customers and designers are eager for PV solutions offering total design freedom for seamless integration into everyday life. This trend becomes even more important if the ‘mega city’ development is taken into account: more and more people will live in city environments in the future while classical PV technologies do not offer proper solutions for this context.