Technical Insight
Sunset for silicon?
Lux Research recently reported which up and coming solar technologies will succeed. Compound Semiconductor talks to analyst Fatima Toor to find out more.
As venture capitalist funds for up and coming photovoltaic start-ups dwindle, corporations are already tapping into the wealth of innovation pouring from academic institutions, worldwide.
In her recent report - 'Continuing education: Going back to school for photovoltaic innovation' - business analyst Fatima Toor from Lux Research, outlines how Dow Chemical, for example, has formed myriad partnerships with companies developing novel CIGS solar modules. Meanwhile US-based solar electricity group, REC, is forging links with developers of III-V nanowire-based cells.
"Venture capital funding is on the decline for solar start-ups but the market opportunity is too big to miss," she says. "A select group of far-sighted companies have already engaged with academic institutions to find growth opportunities."
According to Toor, come 2030, current research will have found its way into commercial systems, so PV modules will be much more 'technologically diverse' than today. This spells good news for III-V and CIGS systems, but not all disruptive PV technologies are equal.
As part of her research, Toor looked at a wealth of technologies including next generation crystalline silicon modules, novel III-V based cells and thin film CIGS alternatives, including tandem CIGS and low-cost CZTS. Heavy metal PVs, such as CdS nanowire cells, as well as organic photovoltaics and dye-sensitised solar cells were also considered.
Not surprisingly novel crystalline silicon cell designs held the greatest promise for commercial success, but Toor asserts industry can also expect to see more multi-junction or tandem cells based on III-V and CIGS materials in the modules of tomorrow.
Roadmap for technology adoption of various incumbent and next-generation PV technologies
Hitting targets
Toor predicts that come 2030, only the novel crystalline silicon PV module designs will have reached, or be getting very very close, to $1/W system price target set by the US Department of Energy Sunshot Initiative. "At almost 90%, crystalline silicon modules have the largest manufacturing capacity in the world, and this infrastructure isn't going anywhere," she adds. "To manufacture [novel] crystalline silicon, it will be a case of upgrading your lines... it will be easier to integrate these new designs than alternative long-term technologies."
But silicon aside, III-V on silicon designs that make the most of existing silicon manufacturing capacity to cut costs, also have potential. Here, Toor believes planar multi-junction or tandem junction cells are a safer bet than, for example, GaAs or InP nanowires on silicon.
"Planar III-V on silicon will have lower process costs because no cleaving of the III-V [layers] off the substrate is necessary and the substrate is a cheap silicon wafer compared to expensive GaAs substrates," says Toor.
In contrast, and despite promising research, III-V nanostructures - such as GaAs or InP nanowires - on silicon are not slated to reach commercial viability. According to Toor, nanowire solar cells suffer from recombination losses that reduce conversion efficiencies.
Toor is also watching so-called parallel HCPV III-V designs that use micro-optical structures to split incident light onto several III-V cells and could boost HCPV module efficiencies to 50% by 2030. "The higher module efficiency will decrease the rest of the stock cost," she explains.
Toor also believes thin film PVs based on tandem-junction CIGS cells hold significant potential, but face significant technical hurdles including matching lattice constants through the layers. But as she adds: "Many initiatives will be able to borrow research from other fields such as [conventional] CIGS, multi-junction III-Vs, enabling rapid improvements in efficiency beyond 2030."
As well as tandem-junction CIGS systems, Toor believes modules with CZTS-based cells -that replace relatively expensive indium and gallium active materials with zinc and tin - will reach the necessary cost and efficiency targets to attain commercial success. Meanwhile, relatively low efficiencies will impede the progress of SnS-based thin film PV technologies.
"Cost will always be an important factor so solar has to become cost competitive compared to other [power generation] technologies," says Toor. "Most of the time if you can improve efficiency then [you] reduce the dollar per Watt. But now durability per kWh is also becoming important. So cost, efficiency and lifetime will all play important roles in the future."
Link:
Lux Research report; 'Continuing education: Going back to school for photovoltaic innovation': https://portal.luxresearchinc.com/research/report_excerpt/14324
