New Hampshire, USA -- The past few weeks have seen announcements and de-stealths from several companies all targeting the same part of the solar photovoltaic supply chain: reduce costs by eliminating most of the silicon material and related processes.
Finding ways to use less silicon made a lot more sense a few years ago when the material cost hundreds of dollars per kilogram — then prices nosedived to and below $20/kg, which made many of those ventures not as attractive, and many fell by the wayside. Nevertheless this remains the highest-cost part of the upstream half of the equation, so it's a clear target for further improvements.
Efforts in this area differ, from gas deposition to a molten formation (a la 1366 Technologies) to an implant/cleave process (Twin Creeks and SiGen), but generally they all offer technology that promises to vastly reduce the use of silicon needed in the ballpark of 80-90 percent and eliminate several steps in the process flow, shooting for a sweetspot silicon thickness of a few tens of microns (30-50 or a bit more). Using less silicon means saving costs, simplifying processes, saving time, while still preserving efficiency. Thinner silicon has some issues with fragility and handling, though, so these players also have figured out ways to incorporate carrier substrates and/or other protective layers.
We've seen several recent announcements and updates from companies pursuing the model of using far less silicon. Here's four of the newest crop of "kerfless" wafer companies, who have a number of things in common, points out Fatima Toor, lead analyst for solar components at Lux Research. They all are based on high-temperature (1000-1100°C) chemical vapor deposition of epitaxial silicon, a type of thin crystalline silicon that conducts both laterally and longitudinally, unlike amorphous silicon that only conducts longitudinally. They all have some kind of lift-off process — except Scifiniti which says it needs none). Cell efficiencies range from 21 percent (Solexel, on a full-size 156×156mm area) to around 15 percent (Crystal Solar on a 125×125mm area, and Amberwave on a 1 cm2 area).
How is this race in ultrathin silicon shaping up? Solexel still has plans to get its Malaysian production facility up and running by 2014. Crystal Solar says that over the next 12 months it will demonstrate 19 percent cell efficiency, build several kWs of large-area modules to test for standards certifications, and build a 25-MW pilot factory with an industrial partner. Scifiniti and Amberwave are less far along the commercialization path, Toor says; they "are just getting their hands dirty."