Understanding Solar Energy

Good longread.

What I'd like to have a better understanding of, and I'm hoping to crowdsource here, is exactly how the solar panel cost has come down so precipitously. Part of it is simply manufacture scaling - almost everything is much cheaper in large quantities. But part of it must be a thousand incremental tech advances. Things like the reduced kerf diamond wire saw.

Also of note: I think monocrystalline has won completely? People experimented with all sorts of alternate chemistries and technologies, like ion deposition and the extremely poisonous CIGS, but good old "Czochralski process + slice thinly" has won despite being energy intensive itself.

Perovskites remain an unknown quantity.

The article posted by wolfram74 is part one of two, covering solar PV history up through the early 1980s.

Here's part two of the series with more recent history: https://www.construction-physics.com/p/how-did-solar-power-g...

Even this fairly long two-part discussion misses some of the more important technical developments of the past 20 years.

Converting trichlorosilane to pure silicon via CVD growth in Siemens-type reactors is now much more energy efficient due to changes in rod geometry and heat trapping via reactor design. A significant minority of purified silicon is now manufactured via even more efficient fluidized bed reactors.

The solar industry is dominated by Czochralski process monocrystalline silicon, but it's now continuous Czochralski: multiple crystals grown from a single crucible, recharging the molten silicon over time; the traditional process used a crucible once and then discarded it.

The dominant silicon material has switched from boron doped p-type silicon to gallium doped p-type silicon (mentioned by pfdietz) to phosphorus doped n-type silicon (used by the currently dominant TOPCon cell technology as well as heterojunction (HJT) cells and most back contact cells).

Changes in wafering that you mentioned (like the reduced kerf diamond wire saw) have reduced silicon consumption per wafer and therefore per watt, even holding cell technology constant.

The dominant cell technology has moved from Al-BSF to PERC to mono-PERC to TOPCon. Heterojunction and back-contact cells are not yet dominant, but they are manufactured on a multi-gigawatt scale and will probably overtake TOPCon eventually. Each one of these changes has eked out more light conversion efficiency from the same area of silicon.

Cells mostly still use screen-printed contacts made from conductive silver pastes, much like 20 years ago, but there has been continuous evolution of the geometry and composition of applied pastes so that silver consumption per watt is now much lower than it used to be. This is important because silver has the highest cost per kilogram of any material in a typical solar panel, and it's the bottleneck material for plans to expand manufacturing past the terawatt scale.

Wafer, cell, and module manufacturing have become much more automated. That reduced labor costs, increased throughput, and increased uniformity.

Thank you and other commenters for the great rundowns here. I'm interested in a related question and I wonder if you or others could point me in the right direction: why was the mainstream consensus around solar power (and/or batteries) apparently so wrong for so long? More specifically -- and maybe a better question -- why didn't progress in solar and batteries happen sooner?

I'm less interested in blame than in a systems analysis of how in the last half century powerful players seem to have missed the opportunity to start earlier investment in solar and battery technology. Solar and batteries are unique in energy infrastructure, as even any casual observer knows by now, and is certain to change many aspects of politics, industry and culture. It seems an inevitability that energy infrastructure will evolve from large complex components towards small and simple components, and I'm interested in engaging with the history of why "now" is the moment, rather than decades ago.