That a new solar cell broke a record for efficiency isn’t terribly groundbreaking. Incremental improvements happen all the time. But this time, the record cells were built using techniques that are easier to transfer to assembly lines.
The new cells, produced by Kaneka, Corp. in Japan, were 26.3% efficient at converting sunlight into electricity, closing in on the theoretical limit for crystalline silicon solar cells, which is 29%.
Crystalline silicon cells are an old technology, but being well understood and inexpensive to produce, they dominate the market for solar power. That means that any gains in efficiency, provided they’re not achieved using exotic methods, have a good chance of reaching the market.
To reach the new record, scientists and engineers worked on implementing a long list of tweaks. One, for example, involved moving the electrodes from the front of the cell to the back, allowing more light to hit the part of the cell that generates electricity.
The cells are based on what’s called called heterojunction technology, which pairs crystalline silicon with non-crystalline, or amorphous, silicon. This technology prevents recombination, where an electron slides into a positive “hole” in the solar cell rather than first being collected and used. By capturing more electrons, efficiency rises.
John Boyd, reporting for IEEE Spectrum, has more:
Kaneka has been developing thin-film silicon solar cell technology since 1980, and it has been working on heterojunction solar cells since 2009. “One of the key process steps used to fabricate these cells is plasma-enhanced chemical vapor deposition—an industrially applicable process,” Yoshikawa points out.
The biggest challenge the company faced in producing the prototype was obtaining a high degree of balance between the cell’s lifetime and its optical characteristics, while simultaneously reducing its internal resistance.
“Although it is possible to obtain an outstanding value for a single characteristic, it is extremely difficult to balance all three properties to a high degree in one device,” Yoshikawa says.
As with any new type of solar cell, there will certainly be a few—maybe many—years before it can be commercialized. But given that the team focused on using industrially friendly techniques from the start, the delay may be shorter than most other cells face.