With the introduction of the alkali post-deposition treatment (PDT) for the absorber layer in Cu(In,Ga)Se2 (CIGS)-based solar cells, new efficiency records approaching 22% have become feasible. After gallium incorporation, sodium doping and the three-stage process, this is the next milestone on the CIGS roadmap. In this paper the current understanding of how PDT alters the CIGS surface and affects device parameters is illustrated. A comparative study of cell device parameters from ZSW and the evolution of efficiencies from other institutes and companies with and without PDT is presented.
Interdigitated back contact (IBC) Si solar cells can be highly efficient: record efficiencies of up to 25.0%, measured over a cell area of 121cm2, have been demonstrated on IBC solar cells by SunPower. The high efficiencies achieved can be attributed to several advantages of cells of this type, including the absence of front metal grid shading and a reduced series resistance. Several metallization schemes have been reported for IBC cells, including screen-printing pastes, and physical vapour deposition (PVD) metal and Cu plating with a suitable barrier layer. In the IBC process development at imec, upscaling from small-area 2cm × 2cm cells to full-area 15.6cm × 15.6cm cells was carried out. In the first instance the 3μm-thick sputtered Al metallization scheme from the 2cm × 2cm cells was adopted. This resulted in cell efficiencies of up to 21.3%, limited by a fill factor (FF) of 77.4%. Besides the limited conductivity of this metallization, the sputtering of a thick Al layer is not straightforward from an industrial perspective; moreover, an Al cell metallization cannot be easily interconnected during module fabrication. A Cu-plating metallization for the large-area IBC cells was therefore investigated, and the scheme is described in detail in this paper. A suitable thin sputtered seed layer for the plating process was studied and developed; this layer serves as a barrier against Cu and has good contact properties to both n+ and p+ Si. The sputtering of the various materials could cause damage to the underlying
passivation layer and to the Si at the cell level, leading to a lower open-circuit voltage (Voc) and pseudo fill factor (pFF). Reduction of this damage has made it possible to obtain IBC cells with efficiencies of up to 21.9%, measured over the full wafer area of 239cm2.
Parallel dispensing technology as an alternative front-side metallization process for silicon solar cells offers the possibility of increasing cell conversion efficiency by 2% rel. by the use of commercial silver pastes designed for screen-printing technology. This efficiency gain is achieved through a significantly reduced finger width, and hence reduced shading losses, in combination with substantially improved finger homogeneities and high aspect ratios that guarantee sufficient grid conductivity at reduced paste lay-down. In this paper Fraunhofer ISE’s development of a parallel dispensing unit that is integrated into an industrial, inline-feasible platform made by ASYS is discussed. A possible industrial application of the dispensing technology is supported by latest results from pilot processing as well as by basic economic considerations
The passivated emitter and rear contact (PERC) cell design is gaining acceptance in solar cell manufacturing because of its potential for high efficiency with p-type wafers and its easy integration into existing production lines. In terms of PERC mass production, an effective and reliable AlOx deposition tool is the most important aspect that needs to be considered. Light-induced degradation (LID) is a cell efficiency bottleneck because of bulk recombination, even if the silicon surface is well passivated. This paper examines the combination of cell efficiency, AlOx tool choice and LID regeneration as a route to industrializing PERC technology
The mechanical strength of monocrystalline and multicrystalline silicon wafers is mainly dictated by the cracks induced during the wire-sawing process. Different sawing technologies, such as diamond-wire- or slurry-based processes, lead to different strength behaviours of as-cut wafers. Furthermore, the strength is strongly influenced by texturization, and at this stage can be interpreted as the basic strength of a solar cell. The metallization and firing processes determine the final strength and reliability of a solar cell, with the metallization contacts being the root cause of breakage of solar cells, depending on the particular cell concept. This paper gives a comprehensive overview of the typical ranges of strength for as-cut wafers, textured wafers and solar cells, for the two different sawing technologies. Around 100 batches with 4,253 samples were evaluated in the study.
As other entrants in the solar industry scramble to build greater efficiencies into their supply chain, the leading companies focus on manufacturing strengths such as zero-defect quality along the entire supply chain. When it comes to supply chain excellence, the solar industry as a whole is playing catch-up. However, there are players who have already made substantial progress here, having already adopted ‘lean’ practices to eliminate inefficiencies at source. REC, the largest European brand of solar panels and a world leader in the industry, is maintaining its strong position. The company’s practices and principles are explained in detail in this paper.
In this quarterly report we will provide full first-half 2015 analysis that shows a massive shift in the geographical location of planned production plants, as well as details on key capacity announcements in the months of May and June. The analysis of April’s capacity announcements were reported in the previous quarterly report. Despite April announcements being so low, May proved to be a blockbuster month. The return of meaningful solar cell capacity plans reiterates the strength in the recovery and the first attempts for many years by leading PV manufacturers to rebalance cell and module production as next- generation PERC technology leads the cell rebalancing act.
R&D expenditure by major PV module manufacturers showed a remarkable turnaround in 2014. Previous reports had noted, especially in 2013, that R&D spending had not been immune to the PV industry’s period of profitless prosperity and was deemed a discretionary spend by the majority of leading producers. A return to profitability for many in 2014 resulted in a year of new record spending. There was record spending from 11 of the 12 companies covered, with Hanwha Q CELLS' spending actually declining in 2014.
Covering a 1,295-hectare estate mostly of fallow farmland, the world’s largest solar plant sits in the Antelope Valley straddling two counties of California. The Solar Star project has been supplying its full 579MW of capacity to the grid since May this year and it will be announced as offi cially complete before the end of 2015. PV Tech Power explored the designs behind this mammoth installation near Rosamond, California, to investigate what key factors had to be considered when creating a solar plant that can supply electricity to more than a quarter of a million homes.
So far in 2015 Chinese domestic PV deployment has outstripped last year’s rates and a possible 20GW has been mooted for the year. This would set a benchmark for China’s new five-year plan for solar development due to come into effect next year, writes Frank Haugwitz.
